diff --git a/shader/common.h b/shader/common.h
index 16704c4a..a34ef548 100644
--- a/shader/common.h
+++ b/shader/common.h
@@ -1,6 +1,9 @@
 #ifdef GLSLES
 
+#ifdef FRAGMENT_SHADER
+/* Only the fragment shader has no default float precision */
 precision mediump float;
+#endif
 
 #else
 
diff --git a/shader/lanczos3.frag b/shader/lanczos3.frag
index 2f84ae85..81225928 100644
--- a/shader/lanczos3.frag
+++ b/shader/lanczos3.frag
@@ -2,6 +2,7 @@
 // Copyright 2020 Lilian Gimenez (Sentmoraap).
 // MIT license.
 
+precision highp float;
 uniform sampler2D texture;
 uniform vec2 sourceSize;
 uniform vec2 texSizeInv;