diff --git a/Diamond/Buffers/Buffer.cs b/Diamond/Buffers/Buffer.cs
index 28142c2..6e8af2e 100644
--- a/Diamond/Buffers/Buffer.cs
+++ b/Diamond/Buffers/Buffer.cs
@@ -78,9 +78,9 @@ namespace Diamond.Buffers
             Wrapper.Bind();
             foreach (var attr in _vdi.Pointers)
             {
-                var loc = program.AttributeLocation(attr.Name);
-                if (loc.HasValue)
-                    GL.VertexAttribPointer((int) loc, attr.Size, attr.Type, attr.Normalized, _vdi.Stride, attr.Offset);
+                if (program.HasAttribute(attr.Name))
+                    GL.VertexAttribPointer(program.AttributeLocation(attr.Name), attr.Size, attr.Type, attr.Normalized,
+                        _vdi.Stride, attr.Offset);
             }
         }
 
diff --git a/Diamond/Buffers/VertexDataInfo.cs b/Diamond/Buffers/VertexDataInfo.cs
index 8e7fd7d..0989f83 100644
--- a/Diamond/Buffers/VertexDataInfo.cs
+++ b/Diamond/Buffers/VertexDataInfo.cs
@@ -51,11 +51,11 @@ namespace Diamond.Buffers
 
             foreach (var attr in Pointers)
             {
-                var loc = Program.Current.AttributeLocation(attr.Name);
-                if (!loc.HasValue)
+                if (!Program.Current.HasAttribute(attr.Name))
                     continue;
-                GL.EnableVertexAttribArray((int) loc);
-                GL.VertexAttribDivisor((int) loc, Divisor);
+                var loc = Program.Current.AttributeLocation(attr.Name);
+                GL.EnableVertexAttribArray(loc);
+                GL.VertexAttribDivisor(loc, Divisor);
             }
         }
 
@@ -69,10 +69,10 @@ namespace Diamond.Buffers
 
             foreach (var attr in Pointers)
             {
-                var loc = Program.Current.AttributeLocation(attr.Name);
-                if (!loc.HasValue)
+                if (!Program.Current.HasAttribute(attr.Name))
                     continue;
-                GL.DisableVertexAttribArray((int) loc);
+                var loc = Program.Current.AttributeLocation(attr.Name);
+                GL.DisableVertexAttribArray(loc);
             }
         }
 
diff --git a/Diamond/Render/RenderGroup.cs b/Diamond/Render/RenderGroup.cs
index 4a40e26..8a3e928 100644
--- a/Diamond/Render/RenderGroup.cs
+++ b/Diamond/Render/RenderGroup.cs
@@ -45,16 +45,12 @@ namespace Diamond.Render
 
             Texture.Bind(0);
 
-            var texLoc = Program.UniformLocation("tex");
-            var viewLoc = Program.UniformLocation("view");
-            var projLoc = Program.UniformLocation("proj");
-
-            if (texLoc.HasValue)
-                GL.Uniform1(texLoc.Value, 0);
-            if (viewLoc.HasValue)
-                GL.UniformMatrix4(viewLoc.Value, false, ref Camera.View);
-            if (projLoc.HasValue)
-                GL.UniformMatrix4(projLoc.Value, false, ref Camera.Projection);
+            if (Program.HasUniform("tex"))
+                GL.Uniform1(Program.UniformLocation("tex"), 0);
+            if (Program.HasUniform("view"))
+                GL.UniformMatrix4(Program.UniformLocation("view"), false, ref Camera.View);
+            if (Program.HasUniform("proj"))
+                GL.UniformMatrix4(Program.UniformLocation("proj"), false, ref Camera.Projection);
 
             if (Instance != null)
                 Vertices.DrawInstanced(Instance);
diff --git a/Diamond/Shaders/Program.cs b/Diamond/Shaders/Program.cs
index 86f990e..0095e35 100644
--- a/Diamond/Shaders/Program.cs
+++ b/Diamond/Shaders/Program.cs
@@ -28,28 +28,46 @@ namespace Diamond.Shaders
             Name = name;
         }
 
-        // todo change these to not use int? - possibly use TryGet, or return negative value if not present
+        /// <summary>
+        /// Check if the program has a uniform
+        /// </summary>
+        /// <param name="name">The name of the uniform</param>
+        /// <returns>Whether the program has this uniform</returns>
+        public bool HasUniform(string name)
+        {
+            return _uniforms.ContainsKey(name);
+        }
 
         /// <summary>
         /// Get the location of a uniform
         /// </summary>
         /// <param name="name">The name of the uniform</param>
-        /// <returns>The location, or no value if uniform not present</returns>
-        public int? UniformLocation(string name)
+        /// <returns>The location of the uniform</returns>
+        public int UniformLocation(string name)
         {
-            if (_uniforms.ContainsKey(name)) return _uniforms[name];
-            return null;
+            if (HasUniform(name)) return _uniforms[name];
+            throw new KeyNotFoundException($"Shader {this} does not contain uniform {name}");
+        }
+
+        /// <summary>
+        /// Check if the program has an attribute
+        /// </summary>
+        /// <param name="name">The name of the attribute</param>
+        /// <returns>Whether the program has this attribute</returns>
+        public bool HasAttribute(string name)
+        {
+            return _attributes.ContainsKey(name);
         }
 
         /// <summary>
         /// Get the location of an attribute
         /// </summary>
         /// <param name="name">The name of the attribute</param>
-        /// <returns>The location, or no value if attribute not present</returns>
-        public int? AttributeLocation(string name)
+        /// <returns>The location of the attribute</returns>
+        public int AttributeLocation(string name)
         {
-            if (_attributes.ContainsKey(name)) return _attributes[name];
-            return null;
+            if (HasAttribute(name)) return _attributes[name];
+            throw new KeyNotFoundException($"Shader {this} does not contain attribute {name}");
         }
 
         /// <summary>