diff --git a/converter/pbm/cmuwmtopbm.c b/converter/pbm/cmuwmtopbm.c
index 5c138c1..1f9bc6c 100644
--- a/converter/pbm/cmuwmtopbm.c
+++ b/converter/pbm/cmuwmtopbm.c
@@ -48,20 +48,20 @@ readCmuwmHeader(FILE *         const ifP,
 
     rc = pm_readbiglong(ifP, &l);
     if (rc == -1 )
-        pm_error(initReadError);
+        pm_error("%s", initReadError);
     if ((uint32_t)l != cmuwmMagic)
         pm_error("bad magic number in CMU window manager file");
     rc = pm_readbiglong(ifP, &l);
     if (rc == -1)
-        pm_error(initReadError);
+        pm_error("%s", initReadError);
     *colsP = l;
     rc = pm_readbiglong(ifP, &l);
     if (rc == -1 )
-        pm_error(initReadError);
+        pm_error("%s", initReadError);
     *rowsP = l;
     rc = pm_readbigshort(ifP, &s);
     if (rc == -1)
-        pm_error(initReadError);
+        pm_error("%s", initReadError);
     *depthP = s;
 }
 
diff --git a/converter/other/tifftopnm.c b/converter/other/tifftopnm.c
index 3aa2e43..b8ebf39 100644
--- a/converter/other/tifftopnm.c
+++ b/converter/other/tifftopnm.c
@@ -1459,7 +1459,7 @@ convertRasterInMemory(pnmOut *       const pnmOutP,
         int ok;
         ok = TIFFRGBAImageOK(tif, emsg);
         if (!ok) {
-            pm_message(emsg);
+            pm_message("%s", emsg);
             *statusP = CONV_UNABLE;
         } else {
             uint32 * raster;
@@ -1479,14 +1479,14 @@ convertRasterInMemory(pnmOut *       const pnmOutP,
                 
                 ok = TIFFRGBAImageBegin(&img, tif, stopOnErrorFalse, emsg);
                 if (!ok) {
-                    pm_message(emsg);
+                    pm_message("%s", emsg);
                     *statusP = CONV_FAILED;
                 } else {
                     int ok;
                     ok = TIFFRGBAImageGet(&img, raster, cols, rows);
                     TIFFRGBAImageEnd(&img) ;
                     if (!ok) {
-                        pm_message(emsg);
+                        pm_message("%s", emsg);
                         *statusP = CONV_FAILED;
                     } else {
                         *statusP = CONV_DONE;
diff --git a/lib/util/pm_c_util.h b/lib/util/pm_c_util.h
index 01a0765..8f5aa01 100644
--- a/lib/util/pm_c_util.h
+++ b/lib/util/pm_c_util.h
@@ -80,10 +80,10 @@
 #endif
 
 #ifndef TRUE
-  #define TRUE true
+  #define TRUE 1
   #endif
 #ifndef FALSE
-  #define FALSE false
+  #define FALSE 0
   #endif
 
 #define ARRAY_SIZE(x) (sizeof(x)/sizeof(x[0]))
diff --git a/converter/other/fiasco/pnmtofiasco.c b/converter/other/fiasco/pnmtofiasco.c
index d78ff6b..761dac5 100644
--- a/converter/other/fiasco/pnmtofiasco.c
+++ b/converter/other/fiasco/pnmtofiasco.c
@@ -170,7 +170,7 @@ main (int argc, char **argv)
       return 0;
    else
    {
-      fprintf (stderr, fiasco_get_error_message ());
+      fprintf (stderr, "%s", fiasco_get_error_message ());
       fprintf (stderr, "\n");
       return 1;
    }
diff --git a/converter/other/fiasco/params.c b/converter/other/fiasco/params.c
index a4d843a..9659e9f 100644
--- a/converter/other/fiasco/params.c
+++ b/converter/other/fiasco/params.c
@@ -656,7 +656,7 @@ usage (const param_t *params, const char *progname, const char *synopsis,
     fprintf (stderr, "Usage: %s [OPTION]...%s\n", progname,
              non_opt_string ? non_opt_string : " ");
     if (synopsis != NULL)
-        fprintf (stderr, synopsis);
+        fprintf (stderr, "%s\n", synopsis);
     fprintf (stderr, "\n\n");
     fprintf (stderr, "Mandatory or optional arguments to long options "
              "are mandatory or optional\nfor short options too. "