diff --git a/src/egl_context.c b/src/egl_context.c
index 64dcdd6f..4f76d351 100644
--- a/src/egl_context.c
+++ b/src/egl_context.c
@@ -311,6 +311,7 @@ static int extensionSupportedEGL(const char* extension)
 static GLFWglproc getProcAddressEGL(const char* procname)
 {
     _GLFWwindow* window = _glfwPlatformGetTls(&_glfw.contextSlot);
+    assert(window != NULL);
 
     if (window->context.egl.client)
     {
diff --git a/src/glx_context.c b/src/glx_context.c
index 4406dfd3..f3f4b3ec 100644
--- a/src/glx_context.c
+++ b/src/glx_context.c
@@ -192,6 +192,7 @@ static void swapBuffersGLX(_GLFWwindow* window)
 static void swapIntervalGLX(int interval)
 {
     _GLFWwindow* window = _glfwPlatformGetTls(&_glfw.contextSlot);
+    assert(window != NULL);
 
     if (_glfw.glx.EXT_swap_control)
     {
diff --git a/src/nsgl_context.m b/src/nsgl_context.m
index 878f32ed..de89e421 100644
--- a/src/nsgl_context.m
+++ b/src/nsgl_context.m
@@ -83,11 +83,10 @@ static void swapIntervalNSGL(int interval)
     @autoreleasepool {
 
     _GLFWwindow* window = _glfwPlatformGetTls(&_glfw.contextSlot);
-    if (window)
-    {
-        [window->context.nsgl.object setValues:&interval
-                                  forParameter:NSOpenGLContextParameterSwapInterval];
-    }
+    assert(window != NULL);
+
+    [window->context.nsgl.object setValues:&interval
+                              forParameter:NSOpenGLContextParameterSwapInterval];
 
     } // autoreleasepool
 }
diff --git a/src/wgl_context.c b/src/wgl_context.c
index cfe24b27..08c499ff 100644
--- a/src/wgl_context.c
+++ b/src/wgl_context.c
@@ -332,6 +332,7 @@ static void swapBuffersWGL(_GLFWwindow* window)
 static void swapIntervalWGL(int interval)
 {
     _GLFWwindow* window = _glfwPlatformGetTls(&_glfw.contextSlot);
+    assert(window != NULL);
 
     window->context.wgl.interval = interval;