diff --git a/src/libespeak-ng/compiledata.c b/src/libespeak-ng/compiledata.c
index d58a2262..f32754cf 100644
--- a/src/libespeak-ng/compiledata.c
+++ b/src/libespeak-ng/compiledata.c
@@ -1401,8 +1401,10 @@ static int LoadEnvelope2(FILE *f, const char *fname)
 			n_points++;
 		}
 	}
-	env_x[n_points] = env_x[n_points-1];
-	env_y[n_points] = env_y[n_points-1];
+	if (n_points > 0) {
+		env_x[n_points] = env_x[n_points-1];
+		env_y[n_points] = env_y[n_points-1];
+	}
 
 	ix = -1;
 	ix2 = 0;