diff --git a/src/backend/gl/glx.c b/src/backend/gl/glx.c
index 40cf9d2..51a82b2 100644
--- a/src/backend/gl/glx.c
+++ b/src/backend/gl/glx.c
@@ -54,8 +54,8 @@ struct _glx_data {
 
 struct glx_fbconfig_info *
 glx_find_fbconfig(Display *dpy, int screen, struct glx_fbconfig_criteria m) {
-	log_debug("Looking for FBConfig for RGBA%d%d%d%d, depth %d", m.red_size, m.blue_size,
-	          m.green_size, m.alpha_size, m.visual_depth);
+	log_debug("Looking for FBConfig for RGBA%d%d%d%d, depth %d", m.red_size,
+	          m.blue_size, m.green_size, m.alpha_size, m.visual_depth);
 
 	int ncfg;
 	// clang-format off
@@ -130,15 +130,18 @@ glx_find_fbconfig(Display *dpy, int screen, struct glx_fbconfig_criteria m) {
 		// All check passed, we are using this one.
 		found = true;
 		ret = cfg[i];
-		glXGetFBConfigAttribChecked(dpy, cfg[i], GLX_BIND_TO_TEXTURE_TARGETS_EXT, &texture_tgts);
+		glXGetFBConfigAttribChecked(dpy, cfg[i], GLX_BIND_TO_TEXTURE_TARGETS_EXT,
+		                            &texture_tgts);
 		glXGetFBConfigAttribChecked(dpy, cfg[i], GLX_Y_INVERTED_EXT, &y_inverted);
 
 		// Prefer the texture format with matching alpha, with the other one as
 		// fallback
 		if (m.alpha_size) {
-			texture_fmt = rgba ? GLX_TEXTURE_FORMAT_RGBA_EXT : GLX_TEXTURE_FORMAT_RGB_EXT;
+			texture_fmt = rgba ? GLX_TEXTURE_FORMAT_RGBA_EXT
+			                   : GLX_TEXTURE_FORMAT_RGB_EXT;
 		} else {
-			texture_fmt = rgb ? GLX_TEXTURE_FORMAT_RGB_EXT : GLX_TEXTURE_FORMAT_RGBA_EXT;
+			texture_fmt =
+			    rgb ? GLX_TEXTURE_FORMAT_RGB_EXT : GLX_TEXTURE_FORMAT_RGBA_EXT;
 		}
 		min_cost = depthbuf + stencil + bufsize * (doublebuf + 1);
 	}
@@ -156,28 +159,6 @@ glx_find_fbconfig(Display *dpy, int screen, struct glx_fbconfig_criteria m) {
 	return info;
 }
 
-/**
- * Check if a GLX extension exists.
- */
-static inline bool glx_has_extension(session_t *ps, const char *ext) {
-	const char *glx_exts = glXQueryExtensionsString(ps->dpy, ps->scr);
-	if (!glx_exts) {
-		log_error("Failed get GLX extension list.");
-		return false;
-	}
-
-	int len = strlen(ext);
-	char *found = strstr(glx_exts, ext);
-	if (!found) {
-		log_info("Missing GLX extension %s.", ext);
-		return false;
-	}
-
-	// Make sure extension names are not crazy...
-	assert(found[len] == ' ' || found[len] == 0);
-	return true;
-}
-
 /**
  * @brief Release binding of a texture.
  */
@@ -284,7 +265,7 @@ static void *glx_init(session_t *ps) {
 	}
 
 	// Ensure GLX_EXT_texture_from_pixmap exists
-	if (!glx_has_extension(ps, "GLX_EXT_texture_from_pixmap"))
+	if (!glx_has_extension(ps->dpy, ps->scr, "GLX_EXT_texture_from_pixmap"))
 		goto end;
 
 	// Initialize GLX data structure
@@ -443,7 +424,8 @@ static void *glx_prepare_win(void *backend_data, session_t *ps, win *w) {
 	    0,
 	};
 
-	wd->texture.target = (GLX_TEXTURE_2D_EXT == tex_tgt ? GL_TEXTURE_2D : GL_TEXTURE_RECTANGLE);
+	wd->texture.target =
+	    (GLX_TEXTURE_2D_EXT == tex_tgt ? GL_TEXTURE_2D : GL_TEXTURE_RECTANGLE);
 	wd->texture.y_inverted = fbcfg->y_inverted;
 
 	wd->glpixmap = glXCreatePixmap(ps->dpy, fbcfg->cfg, wd->pixmap, attrs);
diff --git a/src/backend/gl/glx.h b/src/backend/gl/glx.h
index 04cf736..4ffc3a1 100644
--- a/src/backend/gl/glx.h
+++ b/src/backend/gl/glx.h
@@ -63,3 +63,37 @@ x_visual_to_fbconfig_criteria(xcb_connection_t *c, xcb_visualid_t visual) {
 	    .visual_depth = depth,
 	};
 }
+
+/**
+ * Check if a GLX extension exists.
+ */
+static inline bool glx_has_extension(Display *dpy, int screen, const char *ext) {
+	const char *glx_exts = glXQueryExtensionsString(dpy, screen);
+	if (!glx_exts) {
+		log_error("Failed get GLX extension list.");
+		return false;
+	}
+
+	long inlen = strlen(ext);
+	const char *curr = glx_exts;
+	bool match = false;
+	while (curr && !match) {
+		const char *end = strchr(curr, ' ');
+		if (!end) {
+			// Last extension string
+			match = strcmp(ext, curr) == 0;
+		} else if (end - curr == inlen) {
+			// Length match, do match string
+			match = strncmp(ext, curr, end - curr) == 0;
+		}
+		curr = end ? end + 1 : NULL;
+	}
+
+	if (!match) {
+		log_info("Missing GLX extension %s.", ext);
+	} else {
+		log_info("Found GLX extension %s.", ext);
+	}
+
+	return match;
+}
diff --git a/src/opengl.c b/src/opengl.c
index e9115eb..b22de44 100644
--- a/src/opengl.c
+++ b/src/opengl.c
@@ -83,7 +83,7 @@ glx_init(session_t *ps, bool need_render) {
   }
 
   // Ensure GLX_EXT_texture_from_pixmap exists
-  if (need_render && !glx_hasglxext(ps, "GLX_EXT_texture_from_pixmap"))
+  if (need_render && !glx_has_extension(ps->dpy, ps->scr, "GLX_EXT_texture_from_pixmap"))
     goto glx_init_end;
 
   // Initialize GLX data structure
diff --git a/src/opengl.h b/src/opengl.h
index 52b1cd8..fc93f9e 100644
--- a/src/opengl.h
+++ b/src/opengl.h
@@ -26,46 +26,6 @@
 #include <locale.h>
 #include <GL/glx.h>
 
-/**
- * Check if a word is in string.
- */
-static inline bool
-wd_is_in_str(const char *haystick, const char *needle) {
-  if (!haystick)
-    return false;
-
-  assert(*needle);
-
-  const char *pos = haystick - 1;
-  while ((pos = strstr(pos + 1, needle))) {
-    // Continue if it isn't a word boundary
-    if (((pos - haystick) && !isspace(*(pos - 1)))
-        || (strlen(pos) > strlen(needle) && !isspace(pos[strlen(needle)])))
-      continue;
-    return true;
-  }
-
-  return false;
-}
-
-/**
- * Check if a GLX extension exists.
- */
-static inline bool
-glx_hasglxext(session_t *ps, const char *ext) {
-  const char *glx_exts = glXQueryExtensionsString(ps->dpy, ps->scr);
-  if (!glx_exts) {
-    log_error("Failed get GLX extension list.");
-    return false;
-  }
-
-  bool found = wd_is_in_str(glx_exts, ext);
-  if (!found)
-    log_info("Missing GLX extension %s.", ext);
-
-  return found;
-}
-
 bool
 glx_dim_dst(session_t *ps, int dx, int dy, int width, int height, float z,
     GLfloat factor, const region_t *reg_tgt);
diff --git a/src/vsync.c b/src/vsync.c
index 1869147..db5d289 100644
--- a/src/vsync.c
+++ b/src/vsync.c
@@ -9,6 +9,7 @@
 #include "log.h"
 
 #ifdef CONFIG_OPENGL
+#include "backend/gl/glx.h"
 #include "opengl.h"
 #endif
 
@@ -89,7 +90,7 @@ vsync_opengl_init(session_t *ps) {
   if (!ensure_glx_context(ps))
     return false;
 
-  if (!glx_hasglxext(ps, "GLX_SGI_video_sync")) {
+  if (!glx_has_extension(ps->dpy, ps->scr, "GLX_SGI_video_sync")) {
     log_error("Your driver doesn't support SGI_video_sync, giving up.");
     return false;
   }
@@ -119,7 +120,7 @@ vsync_opengl_oml_init(session_t *ps) {
   if (!ensure_glx_context(ps))
     return false;
 
-  if (!glx_hasglxext(ps, "GLX_OML_sync_control")) {
+  if (!glx_has_extension(ps->dpy, ps->scr, "GLX_OML_sync_control")) {
     log_error("Your driver doesn't support OML_sync_control, giving up.");
     return false;
   }
@@ -150,10 +151,10 @@ vsync_opengl_swc_swap_interval(session_t *ps, unsigned int interval) {
     return false;
 
   if (!ps->psglx->glXSwapIntervalProc && !ps->psglx->glXSwapIntervalMESAProc) {
-    if (glx_hasglxext(ps, "GLX_MESA_swap_control")) {
+    if (glx_has_extension(ps->dpy, ps->scr, "GLX_MESA_swap_control")) {
       ps->psglx->glXSwapIntervalMESAProc = (f_SwapIntervalMESA)
         glXGetProcAddress ((const GLubyte *) "glXSwapIntervalMESA");
-    } else if (glx_hasglxext(ps, "GLX_SGI_swap_control")) {
+    } else if (glx_has_extension(ps->dpy, ps->scr, "GLX_SGI_swap_control")) {
       ps->psglx->glXSwapIntervalProc = (f_SwapIntervalSGI)
         glXGetProcAddress ((const GLubyte *) "glXSwapIntervalSGI");
     } else {