diff --git a/src/context.c b/src/context.c
index d32bb5a9..71c9bc03 100644
--- a/src/context.c
+++ b/src/context.c
@@ -490,16 +490,16 @@ GLboolean _glfwIsValidContext(const _GLFWctxconfig* ctxconfig)
     return GL_TRUE;
 }
 
-int _glfwStringInExtensionString(const char* string, const GLubyte* extensions)
+int _glfwStringInExtensionString(const char* string, const char* extensions)
 {
-    const GLubyte* start = extensions;
+    const char* start = extensions;
 
     for (;;)
     {
-        GLubyte* where;
-        GLubyte* terminator;
+        const char* where;
+        const char* terminator;
 
-        where = (GLubyte*) strstr((const char*) start, string);
+        where = strstr(start, string);
         if (!where)
             return GL_FALSE;
 
@@ -602,7 +602,7 @@ GLFWAPI int glfwExtensionSupported(const char* extension)
     {
         // Check if extension is in the old style OpenGL extensions string
 
-        const GLubyte* extensions = glGetString(GL_EXTENSIONS);
+        const char* extensions = (const char*) glGetString(GL_EXTENSIONS);
         if (!extensions)
         {
             _glfwInputError(GLFW_PLATFORM_ERROR,
diff --git a/src/egl_context.c b/src/egl_context.c
index d6226238..c2c541f0 100644
--- a/src/egl_context.c
+++ b/src/egl_context.c
@@ -476,12 +476,10 @@ void _glfwPlatformSwapInterval(int interval)
 
 int _glfwPlatformExtensionSupported(const char* extension)
 {
-    const char* extensions;
-
-    extensions = eglQueryString(_glfw.egl.display, EGL_EXTENSIONS);
-    if (extensions != NULL)
+    const char* extensions = eglQueryString(_glfw.egl.display, EGL_EXTENSIONS);
+    if (extensions)
     {
-        if (_glfwStringInExtensionString(extension, (unsigned char*) extensions))
+        if (_glfwStringInExtensionString(extension, extensions))
             return GL_TRUE;
     }
 
diff --git a/src/glx_context.c b/src/glx_context.c
index b2c8e7e3..79d6eb5e 100644
--- a/src/glx_context.c
+++ b/src/glx_context.c
@@ -509,10 +509,8 @@ void _glfwPlatformSwapInterval(int interval)
 
 int _glfwPlatformExtensionSupported(const char* extension)
 {
-    const GLubyte* extensions =
-        (const GLubyte*) glXQueryExtensionsString(_glfw.x11.display,
-                                                  _glfw.x11.screen);
-
+    const char* extensions = glXQueryExtensionsString(_glfw.x11.display,
+                                                      _glfw.x11.screen);
     if (extensions)
     {
         if (_glfwStringInExtensionString(extension, extensions))
diff --git a/src/internal.h b/src/internal.h
index 986f6230..80038c63 100644
--- a/src/internal.h
+++ b/src/internal.h
@@ -799,7 +799,7 @@ void _glfwSplitBPP(int bpp, int* red, int* green, int* blue);
  *  @return `GL_TRUE` if the extension was found, or `GL_FALSE` otherwise.
  *  @ingroup utility
  */
-int _glfwStringInExtensionString(const char* string, const GLubyte* extensions);
+int _glfwStringInExtensionString(const char* string, const char* extensions);
 
 /*! @brief Chooses the framebuffer config that best matches the desired one.
  *  @param[in] desired The desired framebuffer config.
diff --git a/src/wgl_context.c b/src/wgl_context.c
index 7514ac6d..e76f3cf7 100644
--- a/src/wgl_context.c
+++ b/src/wgl_context.c
@@ -605,14 +605,14 @@ void _glfwPlatformSwapInterval(int interval)
 
 int _glfwPlatformExtensionSupported(const char* extension)
 {
-    const GLubyte* extensions;
+    const char* extensions;
 
     _GLFWwindow* window = _glfwPlatformGetCurrentContext();
 
     if (window->wgl.GetExtensionsStringEXT != NULL)
     {
-        extensions = (GLubyte*) window->wgl.GetExtensionsStringEXT();
-        if (extensions != NULL)
+        extensions = window->wgl.GetExtensionsStringEXT();
+        if (extensions)
         {
             if (_glfwStringInExtensionString(extension, extensions))
                 return GL_TRUE;
@@ -621,8 +621,8 @@ int _glfwPlatformExtensionSupported(const char* extension)
 
     if (window->wgl.GetExtensionsStringARB != NULL)
     {
-        extensions = (GLubyte*) window->wgl.GetExtensionsStringARB(window->wgl.dc);
-        if (extensions != NULL)
+        extensions = window->wgl.GetExtensionsStringARB(window->wgl.dc);
+        if (extensions)
         {
             if (_glfwStringInExtensionString(extension, extensions))
                 return GL_TRUE;