diff --git a/src/libz/zutil.c b/src/libz/zutil.c
index 8bab6e605..a5f0034de 100644
--- a/src/libz/zutil.c
+++ b/src/libz/zutil.c
@@ -49,7 +49,7 @@ uLong ZEXPORT zlibCompileFlags()
     case 8:     flags += 2 << 6;        break;
     default:    flags += 3 << 6;
     }
-#ifdef DEBUG
+#ifdef PCDEBUG
     flags += 1 << 8;
 #endif
 #if defined(ASMV) || defined(ASMINF)
@@ -103,7 +103,7 @@ uLong ZEXPORT zlibCompileFlags()
     return flags;
 }
 
-#ifdef DEBUG
+#ifdef PCDEBUG
 
 #  ifndef verbose
 #    define verbose 0
diff --git a/src/libz/zutil.h b/src/libz/zutil.h
index 43ee44065..872ef9777 100644
--- a/src/libz/zutil.h
+++ b/src/libz/zutil.h
@@ -227,7 +227,7 @@ extern const char * const z_errmsg[10]; /* indexed by 2-zlib_error */
 #endif
 
 /* Diagnostic functions */
-#ifdef DEBUG
+#ifdef PCDEBUG
 #  include <stdio.h>
    extern int z_verbose;
    extern void z_error    OF((char *m));