diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index bb46831..055c3d6 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -1,62 +1,143 @@
-name: Continuous Integration
+name: CI
 
-on: [push, pull_request]
+on:
+  pull_request:
+  push:
+
+env:
+  RUSTFLAGS: -Dwarnings
 
 jobs:
-  build_test_format_lint:
-    name: ${{matrix.command.name}} (${{matrix.toolchain}})
-    runs-on: ubuntu-latest
-
+  precheck_default:
+    name: Check default
+    runs-on: ${{ matrix.os }}
     strategy:
-      fail-fast: false
       matrix:
-        toolchain: [stable, beta, nightly, 1.46.0]
-        command:
-          - name: Check
-            command: check
-            args: --all-features
-            components: ""
-          - name: Test
-            command: test
-            args: --all-features
-            components: ""
-        include:
-          - toolchain: nightly
-            command:
-              name: Format
-              command: fmt
-              args: --all -- --check
-              components: rustfmt
-          - toolchain: nightly
-            command:
-              name: Lint
-              command: clippy
-              args: --all-features --tests --benches
-              components: clippy
-          - toolchain: stable
-            command:
-              name: Sync readme
-              command: sync-readme
-              args: --check
+        os: [ubuntu-latest]
+        rust: [stable]
 
     steps:
-      - uses: actions/checkout@v2
-      - name: ⚡ Cache
-        uses: actions/cache@v2
-        with:
-          path: |
-            ~/.cargo/registry
-            ~/.cargo/git
-            target
-          key: ${{ runner.os }}-cargo-${{ hashFiles('**/Cargo.lock') }}
+      - uses: actions/checkout@master
 
-      - name: Install toolchain
+      - name: Install ${{ matrix.rust }}
         uses: actions-rs/toolchain@v1
         with:
-          toolchain: ${{ matrix.toolchain }}
+          toolchain: ${{ matrix.rust }}
           override: true
-          default: true
-          components: ${{matrix.command.components}}
+
+      - name: Rust cache
+        uses: Swatinem/rust-cache@v2
+        with:
+          key: ${{ matrix.os }}
+
+      - name: Check
+        uses: actions-rs/cargo@v1
+        with:
+          command:  check
+          args: --all --bins --examples --lib
+
+  precheck_all_features:
+    name: Check all features
+    runs-on: ${{ matrix.os }}
+    strategy:
+      matrix:
+        os: [ubuntu-latest]
+        rust: [stable]
+
+    steps:
+      - uses: actions/checkout@master
+
+      - name: Install ${{ matrix.rust }}
+        uses: actions-rs/toolchain@v1
+        with:
+          toolchain: ${{ matrix.rust }}
+          override: true
+
+      - name: Rust cache
+        uses: Swatinem/rust-cache@v2
+        with:
+          key: ${{ matrix.os }}
+
+      - name: Check
+        uses: actions-rs/cargo@v1
+        with:
+          command:  check
+          args: --all-features --all --bins --examples --tests --lib
+
+  check_msrv:
+    needs: [precheck_default, precheck_all_features]
+    name: Check MSRV with all features
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@master
+
+      - name: Install MSRV toolchain
+        uses: actions-rs/toolchain@v1
+        with:
+          toolchain: 1.56.1
+          override: true
+
+      - name: Rust cache
+        uses: Swatinem/rust-cache@v2
+
+      - name: Check
+        uses: actions-rs/cargo@v1
+        with:
+          command: check
+          args: --all-features --all --bins --examples --tests --lib
+
+  check_benches:
+    needs: [precheck_default, precheck_all_features]
+    name: Check benches with all features
+    runs-on: ${{ matrix.os }}
+    strategy:
+      matrix:
+        os: [ ubuntu-latest ]
+        rust: [ nightly ]
+
+    steps:
+      - uses: actions/checkout@master
+
+      - name: Install ${{ matrix.rust }}
+        uses: actions-rs/toolchain@v1
+        with:
+          toolchain: ${{ matrix.rust }}
+          override: true
+
+      - name: Rust cache
+        uses: Swatinem/rust-cache@v2
+        with:
+          key: ${{ matrix.os }}
+
+      - name: Check
+        uses: actions-rs/cargo@v1
+        with:
+          command: check
+          args: --all-features --all --bins --benches --examples --tests --lib
+
+  check_sync_readme:
+    needs: [precheck_default, precheck_all_features]
+    name: Check sync readme
+    runs-on: ${{ matrix.os }}
+    strategy:
+      matrix:
+        os: [ ubuntu-latest ]
+        rust: [ stable ]
+
+    steps:
+      - uses: actions/checkout@master
+
+      - name: Install ${{ matrix.rust }}
+        uses: actions-rs/toolchain@v1
+        with:
+          toolchain: ${{ matrix.rust }}
+          override: true
+
+      - name: Rust cache
+        uses: Swatinem/rust-cache@v2
+        with:
+          key: ${{ matrix.os }}
 
       - name: Install cargo-sync-readme
         uses: actions-rs/cargo@v1
@@ -64,49 +145,93 @@ jobs:
           command: install
           args: cargo-sync-readme
 
-      - name: ${{matrix.command.name}}
+      - name: Sync readme check
         uses: actions-rs/cargo@v1
         with:
-          command: ${{matrix.command.command}}
-          args: ${{matrix.command.args}}
+          command: sync-readme
+          args: --check
 
-  coveralls_io:
-    name: Coverage
-    runs-on: ubuntu-latest
+  check_platform_compatibility:
+    needs: [precheck_default, precheck_all_features]
+    name: Check platform compatibility
+    runs-on: ${{ matrix.os }}
+    strategy:
+      fail-fast: false
+      matrix:
+        os: [ubuntu-latest, macOS-latest, windows-latest]
+        rust: [stable]
 
     steps:
-      - uses: actions/checkout@v2
-      - name: ⚡ Cache
-        uses: actions/cache@v2
-        with:
-          path: |
-            ~/.cargo/registry
-            ~/.cargo/git
-            target
-          key: ${{ runner.os }}-cargo-${{ hashFiles('**/Cargo.lock') }}
+      - uses: actions/checkout@master
 
-      - name: Install toolchain
+      - name: Install ${{ matrix.rust }}
         uses: actions-rs/toolchain@v1
         with:
-          toolchain: stable
+          toolchain: ${{ matrix.rust }}
           override: true
-          default: true
 
-      - name: Install cargo-tarpaulin
-        uses: actions-rs/install@v0.1
+      - name: Rust cache
+        uses: Swatinem/rust-cache@v2
         with:
-          crate: cargo-tarpaulin
-          version: latest
-          use-tool-cache: true
+          key: ${{ matrix.os }}
 
-      - name: Coverage Report with tarpaulin
+      - name: Check
         uses: actions-rs/cargo@v1
         with:
-          command: tarpaulin
-          args: --all --all-features --out Lcov -- --test-threads 1
+          command:  check
+          args: --all-features --all --bins --examples --tests --lib
 
-      - name: Upload Coverage
-        uses: coverallsapp/github-action@master
+  detailed_tests:
+    needs: [precheck_default, precheck_all_features]
+    name: Check, test, doc, format and lint with all features
+    runs-on: ${{ matrix.os }}
+    strategy:
+      fail-fast: false
+      matrix:
+        os: [ubuntu-latest]
+        rust: [stable, beta, nightly]
+
+    steps:
+      - uses: actions/checkout@master
+
+      - name: Install ${{ matrix.rust }}
+        uses: actions-rs/toolchain@v1
         with:
-          github-token: ${{ secrets.GITHUB_TOKEN }}
-          path-to-lcov: ./lcov.info
\ No newline at end of file
+          toolchain: ${{ matrix.rust }}
+          components: rustfmt, clippy
+          override: true
+
+      - name: Rust cache
+        uses: Swatinem/rust-cache@v2
+        with:
+          key: ${{ matrix.os }}
+
+      - name: Check
+        uses: actions-rs/cargo@v1
+        with:
+          command:  check
+          args: --all-features --all --bins --examples --tests --lib
+
+      - name: Test
+        uses: actions-rs/cargo@v1
+        with:
+          command: test
+          args: --all-features --all
+
+      - name: Docs
+        uses: actions-rs/cargo@v1
+        with:
+          command: doc
+          args: --all-features
+
+      - name: Format
+        uses: actions-rs/cargo@v1
+        with:
+          command: fmt
+          args: -- --check
+
+      - name: Lint
+        uses: actions-rs/cargo@v1
+        with:
+          command: clippy
+          args: --all-features --bins --examples --tests --lib
\ No newline at end of file
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 9e0c473..6164f3f 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -16,6 +16,19 @@
 
 ### Contributors
 
+## [9.0.0](https://github.com/ISibboI/evalexpr/compare/8.2.0...9.0.0) - 2023-04-13
+
+### Fixed
+
+ * Taking numbers to negative powers gave unexpected results (#120)
+ * **Update MSRV to 1.56.1 (2021 edition release)** to allow builds with the latest versions of all dependencies.
+
+### Contributors
+
+My warmhearted thanks goes to:
+
+ * [Pham Nhat Huy](https://github.com/012e)
+
 ## [8.2.0](https://github.com/ISibboI/evalexpr/compare/8.1.0...8.2.0) - 2023-04-13
 
 ### Added
@@ -30,8 +43,8 @@
 
 My warmhearted thanks goes to:
 
-* [Natan Freeman](https://github.com/NatanFreeman)
-* [Claus Matzinger](https://github.com/celaus)
+ * [Natan Freeman](https://github.com/NatanFreeman)
+ * [Claus Matzinger](https://github.com/celaus)
 
 ## [8.1.0](https://github.com/ISibboI/evalexpr/compare/8.0.0...8.1.0) - 2022-07-22
 
diff --git a/Cargo.toml b/Cargo.toml
index 2e38a1e..3ff05fe 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -11,7 +11,7 @@ documentation = "https://docs.rs/evalexpr"
 readme = "README.md"
 license = "MIT"
 edition = "2018"
-rust-version = "1.46.0"
+rust-version = "1.56.1"
 
 [badges]
 maintenance = { status = "actively-developed" }
diff --git a/src/operator/mod.rs b/src/operator/mod.rs
index 5f2be51..13920e1 100644
--- a/src/operator/mod.rs
+++ b/src/operator/mod.rs
@@ -173,6 +173,11 @@ impl Operator {
         }
     }
 
+    /// Returns true if this operator is unary, i.e. it requires exactly one argument.
+    pub(crate) fn is_unary(&self) -> bool {
+        self.max_argument_amount() == Some(1) && *self != Operator::RootNode
+    }
+
     /// Evaluates the operator with the given arguments and context.
     pub(crate) fn eval<C: Context>(
         &self,
diff --git a/src/tree/mod.rs b/src/tree/mod.rs
index c225994..347f787 100644
--- a/src/tree/mod.rs
+++ b/src/tree/mod.rs
@@ -459,8 +459,13 @@ impl Node {
     }
 
     fn insert_back_prioritized(&mut self, node: Node, is_root_node: bool) -> EvalexprResult<()> {
-        // println!("Inserting {:?} into {:?}", node.operator, self.operator());
-        if self.operator().precedence() < node.operator().precedence() || is_root_node
+        // println!(
+        //     "Inserting {:?} into {:?}, is_root_node = {is_root_node}",
+        //     node.operator(),
+        //     self.operator()
+        // );
+        // println!("Self is {:?}", self);
+        if self.operator().precedence() < node.operator().precedence() || node.operator().is_unary() || is_root_node
             // Right-to-left chaining
             || (self.operator().precedence() == node.operator().precedence() && !self.operator().is_left_to_right() && !node.operator().is_left_to_right())
         {
@@ -471,12 +476,15 @@ impl Node {
                 let last_child_operator = self.children.last().unwrap().operator();
 
                 if last_child_operator.precedence()
-                    < node.operator().precedence()
+                    < node.operator().precedence() || node.operator().is_unary()
                     // Right-to-left chaining
                     || (last_child_operator.precedence()
                     == node.operator().precedence() && !last_child_operator.is_left_to_right() && !node.operator().is_left_to_right())
                 {
-                    // println!("Recursing into {:?}", self.children.last().unwrap().operator());
+                    // println!(
+                    //     "Recursing into {:?}",
+                    //     self.children.last().unwrap().operator()
+                    // );
                     // Unwrap cannot fail because is_leaf being false and has_enough_children being true implies that the operator wants and has at least one child
                     self.children
                         .last_mut()
diff --git a/tests/integration.rs b/tests/integration.rs
index 6748fe3..5786f2f 100644
--- a/tests/integration.rs
+++ b/tests/integration.rs
@@ -2145,3 +2145,14 @@ fn test_variable_assignment_and_iteration() {
     variables.sort_unstable();
     assert_eq!(variables, vec!["a".to_string(), "b".to_string()],);
 }
+
+#[test]
+fn test_negative_power() {
+    println!("{:?}", build_operator_tree("3^-2").unwrap());
+    assert_eq!(eval("3^-2"), Ok(Value::Float(1.0 / 9.0)));
+    assert_eq!(eval("3^(-2)"), Ok(Value::Float(1.0 / 9.0)));
+    assert_eq!(eval("-3^2"), Ok(Value::Float(-9.0)));
+    assert_eq!(eval("-(3)^2"), Ok(Value::Float(-9.0)));
+    assert_eq!(eval("(-3)^-2"), Ok(Value::Float(1.0 / 9.0)));
+    assert_eq!(eval("-(3^-2)"), Ok(Value::Float(-1.0 / 9.0)));
+}