diff --git a/clang-tools-extra/include-cleaner/lib/Record.cpp b/clang-tools-extra/include-cleaner/lib/Record.cpp
--- a/clang-tools-extra/include-cleaner/lib/Record.cpp
+++ b/clang-tools-extra/include-cleaner/lib/Record.cpp
@@ -144,9 +144,13 @@
 // FIXME: this is a mirror of clang::clangd::parseIWYUPragma, move to libTooling
 // to share the code?
 static llvm::Optional<StringRef> parseIWYUPragma(const char *Text) {
-  assert(strncmp(Text, "//", 2) || strncmp(Text, "/*", 2));
+  // Skip the comment start, // or /*.
+  if (Text[0] != '/' || (Text[1] != '/' && Text[1] != '*'))
+    return llvm::None;
+  Text += 2;
+
+  // Per spec, direcitves are whitespace- and case-sensitive.
   constexpr llvm::StringLiteral IWYUPragma = " IWYU pragma: ";
-  Text += 2; // Skip the comment start, // or /*.
   if (strncmp(Text, IWYUPragma.data(), IWYUPragma.size()))
     return llvm::None;
   Text += IWYUPragma.size();