diff --git a/src/internal/perk_output_impl.h b/src/internal/perk_output_impl.h
index 62f0322..0fd3c53 100644
--- a/src/internal/perk_output_impl.h
+++ b/src/internal/perk_output_impl.h
@@ -1,3 +1,6 @@
+#ifndef PE_OUTPUT_IMPL_H
+#define PE_OUTPUT_IMPL_H
+
 #include <unistd.h>
 #include <perk/perk.h>
 
@@ -33,3 +36,5 @@ static inline int pe_output_epilog(int ret, FILE * f)
 		fclose(f);
 	return ret;
 }
+
+#endif
diff --git a/src/internal/perk_reader_impl.h b/src/internal/perk_reader_impl.h
index bda7581..9098561 100644
--- a/src/internal/perk_reader_impl.h
+++ b/src/internal/perk_reader_impl.h
@@ -1,5 +1,5 @@
-#ifndef PERK_IMPL_H
-#define PERK_IMPL_H
+#ifndef PERK_READER_IMPL_H
+#define PERK_READER_IMPL_H
 
 #include <stdint.h>
 #include <endian.h>