diff --git a/src/base/URenderer_OpenGL.pas b/src/base/URenderer_OpenGL.pas
index 10bf2f339..7c683f5cd 100644
--- a/src/base/URenderer_OpenGL.pas
+++ b/src/base/URenderer_OpenGL.pas
@@ -77,6 +77,7 @@   TRenderer_OpenGLBase = class(TRenderer)
       SupportsVAO: boolean;
       SupportsFBO: boolean;
       SupportsMappedBuffer: boolean;
+      GlyphTextureFormat: GLint;
 
       MappedBuffer: PGLfloat; // OpenGL 2.0 doesn't support mapped buffers, so we manage it ourself.
 
@@ -284,6 +285,7 @@ implementation
   MAX_QUADS = (VBO_SIZE div QUAD_STRIDE_BYTES); // Number of quads that can be stored in the VBO
   EBO_INDICES = MAX_QUADS * 6; // 2 triangles, 6 total vertices per quad
   EBO_SIZE = EBO_INDICES * SizeOf(GLuint);
+  GL_LUMINANCE = $1909;
 
 type
   TTexture_OpenGL = class(TTexture)
@@ -1523,7 +1525,7 @@ function TRenderer_OpenGLBase.LoadTexture(Data: PByte; W, H: integer; const Iden
 // store this in the red channel, and later assign it to alpha in the fragment shader
 function TRenderer_OpenGLBase.LoadGlyph(Data: PByte; W, H: integer): TTexture;
 begin
-  Result := TTexture_OpenGL.Create(Data, W, H, PATH_NONE, GL_RED, 1, GL_CLAMP_TO_EDGE);
+  Result := TTexture_OpenGL.Create(Data, W, H, PATH_NONE, GlyphTextureFormat, 1, GL_CLAMP_TO_EDGE);
   {$IFDEF DEBUG_MODE}
   RaiseExceptionIfError;
   {$ENDIF};
@@ -1768,6 +1770,7 @@ procedure TRenderer_OpenGL3.CheckVersion();
   SupportsVAO := true;
   SupportsFBO := true;
   SupportsMappedBuffer := true;
+  GlyphTextureFormat := GL_RED;
   if ((MajorVersion > 3) or ((MajorVersion = 3) and (MinorVersion >= 3))) then
     fSupportsProjectM := true;
 end;
@@ -1818,6 +1821,8 @@ procedure TRenderer_OpenGLES.CheckVersion();
 var
   Extensions: string;
   GL_OES_vertex_array_object: boolean;
+  GL_OES_element_index_uint: boolean;
+  GL_EXT_texture_rg: boolean;
 begin
   if (MajorVersion < 2) then
     raise Exception.Create('Could not initialize OpenGL ES 2.0 or later');
@@ -1827,14 +1832,22 @@ procedure TRenderer_OpenGLES.CheckVersion();
     SupportsVAO := true;
     fSupportsProjectM := true;
     SupportsMappedBuffer := true;
+    GlyphTextureFormat := GL_RED;
   end
   else
   begin
     Extensions := Int_GetExtensionString;
+    GL_OES_element_index_uint := Int_CheckExtension(Extensions, 'GL_OES_element_index_uint');
+    if (not GL_OES_element_index_uint) then
+      raise Exception.Create('OpenGL ES driver does not support the required GL_OES_element_index_uint extension');
     GL_OES_vertex_array_object := Int_CheckExtension(Extensions, 'GL_OES_vertex_array_object');
     if (GL_OES_vertex_array_object) then
       SupportsVAO := true;
-
+    GL_EXT_texture_rg := Int_CheckExtension(Extensions, 'GL_EXT_texture_rg');
+    if (GL_EXT_texture_rg) then
+      GlyphTextureFormat := GL_RED
+    else
+      GlyphTextureFormat := GL_LUMINANCE;
   end;
   SupportsFBO := true;
 end;
@@ -1887,6 +1900,7 @@ procedure TRenderer_OpenGL2.CheckVersion();
     SupportsMappedBuffer := true;
   fSupportsProjectM := false;
   SupportsFBO := false;
+  GlyphTextureFormat := GL_LUMINANCE;
 end;
 
 procedure TRenderer_OpenGL2.GetShaderSource(out MainVertex, MainFragment, TextFragment, LineStripVertex, LineStripFragment: string);