diff --git a/src/value/parse.rs b/src/value/parse.rs
index 20646c9..5b2ca2f 100644
--- a/src/value/parse.rs
+++ b/src/value/parse.rs
@@ -529,6 +529,7 @@ impl Value {
         let lower = s.to_ascii_lowercase();
 
         if lower == "progid" && toks.peek().is_some() && toks.peek().unwrap().kind == ':' {
+            s = lower;
             toks.next();
             s.push(':');
             s.push_str(&eat_progid(toks, scope, super_selector)?);
@@ -555,6 +556,7 @@ impl Value {
                     None => {
                         match lower.as_str() {
                             "calc" | "element" | "expression" => {
+                                s = lower;
                                 eat_calc_args(toks, scope, super_selector, &mut s)?;
                             }
                             // "min" => {}
diff --git a/tests/special-functions.rs b/tests/special-functions.rs
index 82fe561..a60452b 100644
--- a/tests/special-functions.rs
+++ b/tests/special-functions.rs
@@ -36,6 +36,16 @@ test!(
     calc_invalid_arithmetic,
     "a {\n  color: calc(2px + 2px + 5%);\n}\n"
 );
+test!(
+    calc_uppercase,
+    "a {\n  color: CALC(1 + 1);\n}\n",
+    "a {\n  color: calc(1 + 1);\n}\n"
+);
+test!(
+    calc_mixed_casing,
+    "a {\n  color: cAlC(1 + 1);\n}\n",
+    "a {\n  color: calc(1 + 1);\n}\n"
+);
 test!(
     element_whitespace,
     "a {\n  color: element(       1      );\n}\n",
@@ -149,3 +159,13 @@ error!(
     progid_number_after_colon,
     "a {\n  color: progid:ap1ple.bottoM..jeans.boots();\n}\n", "Error: expected \"(\"."
 );
+test!(
+    progid_uppercase,
+    "a {\n  color: PROGID:foo(fff);\n}\n",
+    "a {\n  color: progid:foo(fff);\n}\n"
+);
+test!(
+    progid_mixed_casing,
+    "a {\n  color: PrOgId:foo(fff);\n}\n",
+    "a {\n  color: progid:foo(fff);\n}\n"
+);
diff --git a/tests/url.rs b/tests/url.rs
index ed0bf2c..a83b3c3 100644
--- a/tests/url.rs
+++ b/tests/url.rs
@@ -124,3 +124,13 @@ test!(
     "a {\n  color:url(;);\n}\n",
     "a {\n  color: url(;);\n}\n"
 );
+test!(
+    url_uppercase,
+    "a {\n  color: URL(http://foo);\n}\n",
+    "a {\n  color: url(http://foo);\n}\n"
+);
+test!(
+    url_mixed_casing,
+    "a {\n  color: UrL(http://foo);\n}\n",
+    "a {\n  color: url(http://foo);\n}\n"
+);