diff --git a/apps/plugins/puzzles/rbcompat.h b/apps/plugins/puzzles/rbcompat.h
index 4bb9f39ca7..66c86f1cf4 100644
--- a/apps/plugins/puzzles/rbcompat.h
+++ b/apps/plugins/puzzles/rbcompat.h
@@ -15,6 +15,7 @@ double cos_wrapper(double rads);
 int vsprintf_wrapper(char *s, const char *fmt, va_list ap);
 float fabs_wrapper(float n);
 float floor_wrapper(float n);
+int ftoa(char *buf, int len, float f);
 
 float atan_wrapper(float x);
 float atan2_wrapper(float y, float x);
diff --git a/apps/plugins/puzzles/rbwrappers.c b/apps/plugins/puzzles/rbwrappers.c
index 95bc2fc5b1..2d857c1cc9 100644
--- a/apps/plugins/puzzles/rbwrappers.c
+++ b/apps/plugins/puzzles/rbwrappers.c
@@ -23,6 +23,12 @@ int puts_wrapper(const char *s)
     return 0;
 }
 
+int ftoa(char *buf, int len, float f)
+{
+    /* biggest hack ever */
+    return rb->snprintf(buf, len, "%d.%06d", (int)f, (int)((f - (int)f)*1e6));
+}
+
 /* fixed-point wrappers */
 static long lastphase = 0, lastsin = 0, lastcos = 0x7fffffff;
 
diff --git a/apps/plugins/puzzles/src/midend.c b/apps/plugins/puzzles/src/midend.c
index 2eb5ee93e8..6dbdd33905 100644
--- a/apps/plugins/puzzles/src/midend.c
+++ b/apps/plugins/puzzles/src/midend.c
@@ -1701,7 +1701,7 @@ void midend_serialise(midend *me,
      */
     if (me->ourgame->is_timed) {
         char buf[80];
-        sprintf(buf, "%g", me->elapsed);
+        ftoa(buf, 80, me->elapsed);
         wr("TIME", buf);
     }
 
diff --git a/apps/plugins/puzzles/src/net.c b/apps/plugins/puzzles/src/net.c
index de51f82fd7..9289afb682 100644
--- a/apps/plugins/puzzles/src/net.c
+++ b/apps/plugins/puzzles/src/net.c
@@ -257,7 +257,10 @@ static char *encode_params(const game_params *params, int full)
     if (params->wrapping)
         ret[len++] = 'w';
     if (full && params->barrier_probability)
-        len += sprintf(ret+len, "b%g", params->barrier_probability);
+    {
+        len += sprintf(ret+len, "b");
+        len += ftoa(ret + len, 400, params->barrier_probability);
+    }
     if (full && !params->unique)
         ret[len++] = 'a';
     assert(len < lenof(ret));
@@ -292,7 +295,7 @@ static config_item *game_configure(const game_params *params)
 
     ret[3].name = "Barrier probability";
     ret[3].type = C_STRING;
-    sprintf(buf, "%g", params->barrier_probability);
+    ftoa(buf, 80, params->barrier_probability);
     ret[3].sval = dupstr(buf);
     ret[3].ival = 0;
 
diff --git a/apps/plugins/puzzles/src/netslide.c b/apps/plugins/puzzles/src/netslide.c
index c56e1abd6a..663febc61a 100644
--- a/apps/plugins/puzzles/src/netslide.c
+++ b/apps/plugins/puzzles/src/netslide.c
@@ -241,7 +241,10 @@ static char *encode_params(const game_params *params, int full)
     if (params->wrapping)
         ret[len++] = 'w';
     if (full && params->barrier_probability)
-        len += sprintf(ret+len, "b%g", params->barrier_probability);
+    {
+        len += sprintf(ret+len, "b");
+        len += ftoa(ret + len, 400, params->barrier_probability);
+    }
     /* Shuffle limit is part of the limited parameters, because we have to
      * provide the target move count. */
     if (params->movetarget)
@@ -278,7 +281,7 @@ static config_item *game_configure(const game_params *params)
 
     ret[3].name = "Barrier probability";
     ret[3].type = C_STRING;
-    sprintf(buf, "%g", params->barrier_probability);
+    ftoa(buf, 80, params->barrier_probability);
     ret[3].sval = dupstr(buf);
     ret[3].ival = 0;
 
diff --git a/apps/plugins/puzzles/src/rect.c b/apps/plugins/puzzles/src/rect.c
index 465e1436fa..0c06c74945 100644
--- a/apps/plugins/puzzles/src/rect.c
+++ b/apps/plugins/puzzles/src/rect.c
@@ -163,7 +163,10 @@ static char *encode_params(const game_params *params, int full)
 
     sprintf(data, "%dx%d", params->w, params->h);
     if (full && params->expandfactor)
-        sprintf(data + strlen(data), "e%g", params->expandfactor);
+    {
+        sprintf(data + strlen(data), "e");
+        ftoa(data + strlen(data), 256, params->expandfactor);
+    }
     if (full && !params->unique)
         strcat(data, "a");
 
@@ -191,7 +194,7 @@ static config_item *game_configure(const game_params *params)
 
     ret[2].name = "Expansion factor";
     ret[2].type = C_STRING;
-    sprintf(buf, "%g", params->expandfactor);
+    ftoa(buf, 80, params->expandfactor);
     ret[2].sval = dupstr(buf);
     ret[2].ival = 0;