diff --git a/CHANGELOG.md b/CHANGELOG.md
index 6bd417c95e..75d927c6e8 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -11,6 +11,7 @@
 - On Wayland, Hide CSD for fullscreen windows.
 - On Windows, ignore spurious mouse move messages.
 - **Breaking:** Move `ModifiersChanged` variant from `DeviceEvent` to `WindowEvent`.
+- On Windows, fix crash at startup on systems that do not properly support Windows' Dark Mode
 
 # 0.21.0 (2020-02-04)
 
diff --git a/src/platform_impl/windows/dark_mode.rs b/src/platform_impl/windows/dark_mode.rs
index c50c4f21af..3c7c16eebf 100644
--- a/src/platform_impl/windows/dark_mode.rs
+++ b/src/platform_impl/windows/dark_mode.rs
@@ -6,9 +6,10 @@ use std::os::windows::ffi::OsStrExt;
 use winapi::{
     shared::{
         basetsd::SIZE_T,
-        minwindef::{BOOL, DWORD, UINT, ULONG, WORD},
+        minwindef::{BOOL, DWORD, FALSE, UINT, ULONG, WORD},
         ntdef::{LPSTR, NTSTATUS, NT_SUCCESS, PVOID, WCHAR},
         windef::HWND,
+        winerror::S_OK,
     },
     um::{libloaderapi, uxtheme, winuser},
 };
@@ -44,9 +45,8 @@ lazy_static! {
                 };
 
                 let status = (rtl_get_version)(&mut vi as _);
-                assert!(NT_SUCCESS(status));
 
-                if vi.dwMajorVersion == 10 && vi.dwMinorVersion == 0 {
+                if NT_SUCCESS(status) && vi.dwMajorVersion == 10 && vi.dwMinorVersion == 0 {
                     Some(vi.dwBuildNumber)
                 } else {
                     None
@@ -82,22 +82,15 @@ pub fn try_dark_mode(hwnd: HWND) -> bool {
             LIGHT_THEME_NAME.as_ptr()
         };
 
-        unsafe {
-            assert_eq!(
-                0,
-                uxtheme::SetWindowTheme(hwnd, theme_name as _, std::ptr::null())
-            );
-
-            set_dark_mode_for_window(hwnd, is_dark_mode)
-        }
+        let status = unsafe { uxtheme::SetWindowTheme(hwnd, theme_name as _, std::ptr::null()) };
 
-        is_dark_mode
+        status == S_OK && set_dark_mode_for_window(hwnd, is_dark_mode)
     } else {
         false
     }
 }
 
-fn set_dark_mode_for_window(hwnd: HWND, is_dark_mode: bool) {
+fn set_dark_mode_for_window(hwnd: HWND, is_dark_mode: bool) -> bool {
     // Uses Windows undocumented API SetWindowCompositionAttribute,
     // as seen in win32-darkmode example linked at top of file.
 
@@ -132,11 +125,12 @@ fn set_dark_mode_for_window(hwnd: HWND, is_dark_mode: bool) {
                 cbData: std::mem::size_of_val(&is_dark_mode_bigbool) as _,
             };
 
-            assert_eq!(
-                1,
-                set_window_composition_attribute(hwnd, &mut data as *mut _)
-            );
+            let status = set_window_composition_attribute(hwnd, &mut data as *mut _);
+
+            status != FALSE
         }
+    } else {
+        false
     }
 }
 
@@ -205,7 +199,7 @@ fn is_high_contrast() -> bool {
         )
     };
 
-    (ok > 0) && ((HCF_HIGHCONTRASTON & hc.dwFlags) == 1)
+    ok != FALSE && (HCF_HIGHCONTRASTON & hc.dwFlags) == 1
 }
 
 fn widestring(src: &'static str) -> Vec<u16> {