diff --git a/src/cocoa_monitor.m b/src/cocoa_monitor.m
index 5ced387e..cfb76a79 100644
--- a/src/cocoa_monitor.m
+++ b/src/cocoa_monitor.m
@@ -326,7 +326,7 @@ void _glfwPlatformGetMonitorPos(_GLFWmonitor* monitor, int* xpos, int* ypos)
 GLFWvidmode* _glfwPlatformGetVideoModes(_GLFWmonitor* monitor, int* found)
 {
     CFArrayRef modes;
-    CFIndex count, i;
+    CFIndex count, i, j;
     GLFWvidmode* result;
     CVDisplayLinkRef link;
 
@@ -340,12 +340,26 @@ GLFWvidmode* _glfwPlatformGetVideoModes(_GLFWmonitor* monitor, int* found)
 
     for (i = 0;  i < count;  i++)
     {
-        CGDisplayModeRef mode = (CGDisplayModeRef) CFArrayGetValueAtIndex(modes, i);
-        if (modeIsGood(mode))
+        CGDisplayModeRef dm = (CGDisplayModeRef) CFArrayGetValueAtIndex(modes, i);
+        if (!modeIsGood(dm))
+            continue;
+
+        const GLFWvidmode mode = vidmodeFromCGDisplayMode(dm, link);
+
+        for (j = 0;  j < *found;  j++)
         {
-            result[*found] = vidmodeFromCGDisplayMode(mode, link);
-            (*found)++;
+            if (_glfwCompareVideoModes(result + j, &mode) == 0)
+                break;
         }
+
+        if (i < *found)
+        {
+            // This is a duplicate, so skip it
+            continue;
+        }
+
+        result[*found] = mode;
+        (*found)++;
     }
 
     CFRelease(modes);
diff --git a/src/x11_monitor.c b/src/x11_monitor.c
index d0bbb434..36d914d6 100644
--- a/src/x11_monitor.c
+++ b/src/x11_monitor.c
@@ -352,12 +352,8 @@ GLFWvidmode* _glfwPlatformGetVideoModes(_GLFWmonitor* monitor, int* found)
 
             for (j = 0;  j < *found;  j++)
             {
-                if (result[j].width == mode.width &&
-                    result[j].height == mode.height &&
-                    result[j].refreshRate == mode.refreshRate)
-                {
+                if (_glfwCompareVideoModes(result + j, &mode) == 0)
                     break;
-                }
             }
 
             if (j < *found)