diff --git a/src/compiler/compile/css/Stylesheet.ts b/src/compiler/compile/css/Stylesheet.ts
index 8f88f0cbd406..0a3098db6d63 100644
--- a/src/compiler/compile/css/Stylesheet.ts
+++ b/src/compiler/compile/css/Stylesheet.ts
@@ -145,6 +145,10 @@ class Declaration {
 			? this.node.value.children[0]
 			: this.node.value;
 
+		// Don't minify whitespace in custom properties, since some browsers (Chromium < 99)
+		// treat --foo: ; and --foo:; differently
+		if (first.type === 'Raw' && /^\s+$/.test(first.value)) return;
+
 		let start = first.start;
 		while (/\s/.test(code.original[start])) start += 1;
 
diff --git a/test/css/samples/css-vars/expected.css b/test/css/samples/css-vars/expected.css
index c2bd56375b1f..d9ff79a2a9c8 100644
--- a/test/css/samples/css-vars/expected.css
+++ b/test/css/samples/css-vars/expected.css
@@ -1 +1 @@
-:root{--root-test:20}div.svelte-xyz{--test:10}
\ No newline at end of file
+:root{--root-test:20}div.svelte-xyz{--test:10}div.svelte-xyz{--foo: ;--bar: !important}
\ No newline at end of file
diff --git a/test/css/samples/css-vars/input.svelte b/test/css/samples/css-vars/input.svelte
index 7aa48617a48b..4a969428ab6d 100644
--- a/test/css/samples/css-vars/input.svelte
+++ b/test/css/samples/css-vars/input.svelte
@@ -7,4 +7,9 @@
 	div {
 		--test: 10;
 	}
+
+	div {
+		--foo: ;
+		--bar: !important;
+	}
 </style>