diff --git a/src/egl_context.c b/src/egl_context.c
index aeadbded..53667bd5 100644
--- a/src/egl_context.c
+++ b/src/egl_context.c
@@ -304,6 +304,7 @@ 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 46f63476..220e3d02 100644
--- a/src/glx_context.c
+++ b/src/glx_context.c
@@ -190,6 +190,7 @@ 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 78d688c4..e984caeb 100644
--- a/src/nsgl_context.m
+++ b/src/nsgl_context.m
@@ -81,11 +81,10 @@ 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 a7704738..eebf6cd5 100644
--- a/src/wgl_context.c
+++ b/src/wgl_context.c
@@ -333,6 +333,7 @@ static void swapBuffersWGL(_GLFWwindow* window)
 static void swapIntervalWGL(int interval)
 {
     _GLFWwindow* window = _glfwPlatformGetTls(&_glfw.contextSlot);
+    assert(window != NULL);
 
     window->context.wgl.interval = interval;