diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 7f1027c..d05a605 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -95,7 +95,12 @@ jobs:
           files: "./dist/*"
 
   docker-test:
+    name: Docker Test gxx${{ matrix.gxx_major }}
     runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        gxx_major: [14, 15]
 
     steps:
       - name: Checkout code
@@ -103,5 +108,5 @@ jobs:
 
       - name: Build and test Docker image
         run: |
-          docker build -t spatial_graph .
+          docker build --build-arg GXX_MAJOR=${{ matrix.gxx_major }} -t spatial_graph .
           docker run --rm spatial_graph
diff --git a/Dockerfile b/Dockerfile
index 349d162..d5d8214 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -4,32 +4,36 @@ ENV DEBIAN_FRONTEND=noninteractive \
     MAMBA_ROOT_PREFIX=/opt/conda \
     PATH=/opt/conda/bin:$PATH
 
+# Allow overriding the major GCC/G++ version at build time (e.g. --build-arg GXX_MAJOR=14)
+ARG GXX_MAJOR=15
+
 RUN apt-get update && \
     apt-get install -y --no-install-recommends \
       git curl tar bzip2 ca-certificates && \
     rm -rf /var/lib/apt/lists/*
 
+
+WORKDIR /app
+COPY . /app
+
 # auto-detect arch and grab the matching micromamba binary
 RUN set -eux; \
     arch="$(uname -m)"; \
     case "$arch" in \
-      x86_64)    url_arch=linux-64 ;; \
-      aarch64|arm64) url_arch=linux-aarch64 ;; \
-      ppc64le)   url_arch=linux-ppc64le ;; \
-      *)         echo "Unsupported arch: $arch"; exit 1 ;; \
+        x86_64)          url_arch=linux-64;      gxx_pkg=gxx_linux-64 ;; \
+        aarch64|arm64)   url_arch=linux-aarch64; gxx_pkg=gxx_linux-aarch64 ;; \
+        ppc64le)         url_arch=linux-ppc64le; gxx_pkg=gxx_linux-ppc64le ;; \
+        *)               echo "Unsupported arch: $arch"; exit 1 ;; \
     esac; \
     curl -Ls "https://micro.mamba.pm/api/micromamba/$url_arch/latest" \
       | tar -xvj -C /usr/local/bin bin/micromamba; \
     chmod +x /usr/local/bin/bin/micromamba; \
     mv /usr/local/bin/bin/micromamba /usr/local/bin/micromamba; \
-    rmdir /usr/local/bin/bin
-
-
-WORKDIR /app
-COPY . /app
+    rmdir /usr/local/bin/bin; \
+    micromamba create -y -n test-env -c conda-forge \
+        python=3.12 pip gxx "${gxx_pkg}=${GXX_MAJOR}.*"; \
+    micromamba run -n test-env pip install -e . --group test
 
-RUN micromamba create -y -n test-env -c conda-forge python=3.12 pip compilers
-RUN micromamba run -n test-env pip install -e . --group test
 
 SHELL ["micromamba", "run", "-n", "test-env", "/bin/bash", "-o", "pipefail", "-c"]
 
diff --git a/src/spatial_graph/_rtree/src/rtree.h b/src/spatial_graph/_rtree/src/rtree.h
index dfa8e73..3217e9d 100644
--- a/src/spatial_graph/_rtree/src/rtree.h
+++ b/src/spatial_graph/_rtree/src/rtree.h
@@ -6,6 +6,7 @@
 #define RTREE_H
 
 #include <stdlib.h>
+#include <stdbool.h>
 #include "config.h"
 
 // rtree_new returns a new rtree
@@ -83,8 +84,8 @@ int rtree_delete(struct rtree *tr, const coord_t *min, const coord_t *max, const
 // rectangle, and perform a comparison of its data to the provided data using
 // a compare function. The first item that is found is deleted.
 //
-// Returns false if the system is out of memory.
-bool rtree_delete_with_comparator(struct rtree *tr, const coord_t *min,
+// Returns the number of deleted items (0 or 1) or -1 if an OOM error occured.
+int rtree_delete_with_comparator(struct rtree *tr, const coord_t *min,
 	const coord_t *max, const item_t item,
 	int (*compare)(const item_t a, const item_t b, void *udata),
 	void *udata);
diff --git a/src/spatial_graph/_rtree/wrapper_template.pyx b/src/spatial_graph/_rtree/wrapper_template.pyx
index f0844b6..c378085 100644
--- a/src/spatial_graph/_rtree/wrapper_template.pyx
+++ b/src/spatial_graph/_rtree/wrapper_template.pyx
@@ -1,19 +1,15 @@
 from libc.stdint cimport *
+from libcpp cimport bool
 import numpy as np
 
-
-ctypedef int bool
-
 cdef extern from *:
     """
-    typedef int bool;
-    #define false 0
-    #define true 1
-
     %if $c_distance_function
     #define KNN_USE_EXACT_DISTANCE
     %end if
     #define DIMS $dims
+    #include <stdbool.h>
+    #include <string.h>
 
     typedef $coord_dtype.to_pyxtype() coord_t;
     typedef $item_dtype.base_c_type item_base_t;
@@ -152,7 +148,7 @@ cdef pyx_items_t memview_to_pyx_items_t($item_dtype.to_pyxtype(add_dim=True) ite
     %end if
 
 
-cdef bint count_iterator(
+cdef bool count_iterator(
         const coord_t* bb_min,
         const coord_t* bb_max,
         const item_t item,
@@ -174,7 +170,7 @@ cdef init_search_results_from_memview(search_results* r, $item_dtype.to_pyxtype(
     r.items = memview_to_pyx_items_t(items)
 
 
-cdef bint search_iterator(
+cdef bool search_iterator(
         const coord_t* bb_min,
         const coord_t* bb_max,
         const item_t item,
@@ -203,7 +199,7 @@ cdef init_nearest_results_from_memview(nearest_results* r,
     r.distances = &distances[0] if distances is not None else NULL
 
 
-cdef bint nearest_iterator(
+cdef bool nearest_iterator(
         const item_t item,
         coord_t distance,
         void* udata