diff --git a/cpuid/x86.hpp b/cpuid/x86.hpp
index 4a3294ac..f707db2b 100644
--- a/cpuid/x86.hpp
+++ b/cpuid/x86.hpp
@@ -15,6 +15,7 @@
 #endif
 
 #include <array>
+#include <iosfwd>
 
 namespace cruft::cpu {
     /// Queries x86 CPU features using the CPUID instruction.