diff --git a/src/gui/rhi/qrhigles2.cpp b/src/gui/rhi/qrhigles2.cpp
index 5208bd4d..a2625949 100644
--- a/src/gui/rhi/qrhigles2.cpp
+++ b/src/gui/rhi/qrhigles2.cpp
@@ -1367,18 +1367,25 @@ static inline void toGlTextureFormat(QRhiTexture::Format format, const QRhiGles2
     case QRhiTexture::RG8:
         *glintformat = GL_RG8;
         *glsizedintformat = *glintformat;
         *glformat = GL_RG;
         *gltype = GL_UNSIGNED_BYTE;
         break;
-    case QRhiTexture::RED_OR_ALPHA8:
-        *glintformat = caps.coreProfile ? GL_R8 : GL_ALPHA;
+    case QRhiTexture::RED_OR_ALPHA8: {
+        // qt6-base-fourier: GL_ALPHA was removed from the valid
+        // glTexImage2D internalFormat list in OpenGL ES 3.0 (ES 3
+        // spec section 3.8.3). Pick GL_R8 + GL_RED for desktop GL
+        // Core profile and for any ES 3 or newer context; only
+        // legacy ES 2 contexts retain GL_ALPHA.
+        const bool useR8 = caps.coreProfile || (caps.gles && caps.ctxMajor >= 3);
+        *glintformat = useR8 ? GL_R8 : GL_ALPHA;
         *glsizedintformat = *glintformat;
-        *glformat = caps.coreProfile ? GL_RED : GL_ALPHA;
+        *glformat = useR8 ? GL_RED : GL_ALPHA;
         *gltype = GL_UNSIGNED_BYTE;
         break;
+    }
     case QRhiTexture::RGBA16F:
         *glintformat = GL_RGBA16F;
         *glsizedintformat = *glintformat;
         *glformat = GL_RGBA;
         *gltype = GL_HALF_FLOAT;
         break;