diff --git a/sdrgui/gui/glshadercolormap.cpp b/sdrgui/gui/glshadercolormap.cpp
index 92dacaa7a..f1d2bb464 100644
--- a/sdrgui/gui/glshadercolormap.cpp
+++ b/sdrgui/gui/glshadercolormap.cpp
@@ -156,7 +156,11 @@ void GLShaderColorMap::drawSurfaceStrip(const QMatrix4x4& transformMatrix, GLflo
     QOpenGLFunctions *f = QOpenGLContext::currentContext()->functions();
     m_program->bind();
     m_program->setUniformValue(m_matrixLoc, transformMatrix);
-    m_colorMapTexture->bind();
+    if (m_useImmutableStorage) {
+        m_colorMapTexture->bind();
+    } else {
+        glBindTexture(GL_TEXTURE_2D, m_colorMapTextureId);
+    }
     m_program->setUniformValue(m_colorMapLoc, 0); // Texture unit 0 for color map
     m_program->setUniformValue(m_scaleLoc, scale);
     m_program->setUniformValue(m_alphaLoc, alpha);
@@ -242,7 +246,7 @@ bool GLShaderColorMap::useImmutableStorage()
 const QString GLShaderColorMap::m_vertexShaderSourceColorMap2 = QString(
         "uniform highp mat4 uMatrix;\n"
         "attribute highp vec4 vertex;\n"
-        "varying float y;\n"
+        "varying highp float y;\n"
         "void main() {\n"
         "    gl_Position = uMatrix * vertex;\n"
         "    y = vertex.y;\n"
@@ -261,10 +265,10 @@ const QString GLShaderColorMap::m_vertexShaderSourceColorMap = QString(
         );
 
 const QString GLShaderColorMap::m_fragmentShaderSourceColorMap2 = QString(
-        "uniform float alpha;\n"
-        "uniform float scale;\n"
+        "uniform highp float alpha;\n"
+        "uniform highp float scale;\n"
         "uniform highp sampler2D colorMap;\n"
-        "varying float y;\n"
+        "varying highp float y;\n"
         "void main() {\n"
         "    gl_FragColor = vec4(texture2D(colorMap, vec2(1.0-(y/scale), 0)).rgb, alpha);\n"
         "}\n"
diff --git a/sdrgui/gui/glshaderspectrogram.cpp b/sdrgui/gui/glshaderspectrogram.cpp
index b20642af1..10d3d0dc4 100644
--- a/sdrgui/gui/glshaderspectrogram.cpp
+++ b/sdrgui/gui/glshaderspectrogram.cpp
@@ -288,6 +288,7 @@ void GLShaderSpectrogram::initTexture(const QImage& image)
         initTextureMutable(image);
     }
     initGrid(image.width());
+    m_limit = 1.4f*1.0f/(float)image.height();
 }
 
 void GLShaderSpectrogram::initTextureImmutable(const QImage& image)
@@ -419,7 +420,7 @@ void GLShaderSpectrogram::drawSurface(SpectrumSettings::SpectrogramStyle style,
     program->setUniformValue(m_dataTextureLoc, 0);         // set uniform to texture unit?
     program->setUniformValue(m_colorMapLoc, 1);
 
-    program->setUniformValue(m_limitLoc, 1.4f*1.0f/(float)(m_texture->height()));
+    program->setUniformValue(m_limitLoc, m_limit);
 
     if (style == SpectrumSettings::Outline)
     {
@@ -721,11 +722,11 @@ void GLShaderSpectrogram::applyPerspective(QMatrix4x4 &matrix)
 const QString GLShaderSpectrogram::m_vertexShader2 = QString(
     "attribute vec2 coord2d;\n"
     "varying vec4 coord;\n"
-    "varying float lightDistance;\n"
+    "varying highp float lightDistance;\n"
     "uniform mat4 textureTransform;\n"
     "uniform mat4 vertexTransform;\n"
     "uniform sampler2D dataTexture;\n"
-    "uniform float limit;\n"
+    "uniform highp float limit;\n"
     "uniform vec3 lightPos;\n"
     "void main(void) {\n"
     "   coord = textureTransform * vec4(clamp(coord2d, limit, 1.0-limit), 0, 1);\n"
@@ -810,11 +811,11 @@ const QString GLShaderSpectrogram::m_fragmentShaderShaded = QString(
     );
 
 const QString GLShaderSpectrogram::m_fragmentShaderSimple2 = QString(
-    "varying vec4 coord;\n"
-    "uniform float brightness;\n"
+    "varying highp vec4 coord;\n"
+    "uniform highp float brightness;\n"
     "uniform sampler2D colorMap;\n"
     "void main(void) {\n"
-    "    float factor;\n"
+    "    highp float factor;\n"
     "    if (gl_FrontFacing)\n"
     "        factor = 1.0;\n"
     "    else\n"
diff --git a/sdrgui/gui/glshaderspectrogram.h b/sdrgui/gui/glshaderspectrogram.h
index 5b196b0c6..35050606c 100644
--- a/sdrgui/gui/glshaderspectrogram.h
+++ b/sdrgui/gui/glshaderspectrogram.h
@@ -81,6 +81,7 @@ private:
     unsigned int m_textureId;
     QOpenGLTexture *m_colorMapTexture;
     unsigned int m_colorMapTextureId;
+    float m_limit;
 
     QOpenGLShaderProgram *m_programForLocs;     // Which program the locations are for
     int m_coord2dLoc;