diff --git a/ggml-opencl.cpp b/ggml-opencl.cpp
index e0b1cb78f..8f2e5fbca 100644
--- a/ggml-opencl.cpp
+++ b/ggml-opencl.cpp
@@ -469,8 +469,9 @@ void ggml_cl_init(void) {
 
     size_t ext_str_size;
     clGetDeviceInfo(device, CL_DEVICE_EXTENSIONS, 0, NULL, &ext_str_size);
-    char *ext_buffer = (char *)alloca(ext_str_size);
+    char *ext_buffer = (char *)alloca(ext_str_size + 1);
     clGetDeviceInfo(device, CL_DEVICE_EXTENSIONS, ext_str_size, ext_buffer, NULL);
+    ext_buffer[ext_str_size] = '\0'; // ensure it is null terminated
     // Check if ext_buffer contains cl_khr_fp16
     fp16_support = strstr(ext_buffer, "cl_khr_fp16") != NULL;
     fprintf(stderr, "ggml_opencl: device FP16 support: %s\n", fp16_support ? "true" : "false");