diff --git a/src/Shader/ShaderCore.cpp b/src/Shader/ShaderCore.cpp
index 883131c..338605c 100644
--- a/src/Shader/ShaderCore.cpp
+++ b/src/Shader/ShaderCore.cpp
@@ -402,14 +402,13 @@
 		Float4 y0 = Abs(y);
 
 		// Rotate to right quadrant when in left quadrant
-		Int4 non_zero_y = CmpNEQ(y0, Float4(0.0f));
-		Int4 Q = CmpLT(x0, Float4(0.0f)) & non_zero_y;
+		Int4 Q = CmpLT(x0, Float4(0.0f));
 		theta += As<Float4>(Q & As<Int4>(half_pi));
 		Float4 x1 = As<Float4>((Q & As<Int4>(y0)) | (~Q & As<Int4>(x0)));  // FIXME: Vector select
 		Float4 y1 = As<Float4>((Q & As<Int4>(-x0)) | (~Q & As<Int4>(y0))); // FIXME: Vector select
 
 		// Mirror to first octant when in second octant
-		Int4 O = CmpNLT(y1, x1) & non_zero_y;
+		Int4 O = CmpNLT(y1, x1);
 		Float4 x2 = As<Float4>((O & As<Int4>(y1)) | (~O & As<Int4>(x1))); // FIXME: Vector select
 		Float4 y2 = As<Float4>((O & As<Int4>(x1)) | (~O & As<Int4>(y1))); // FIXME: Vector select
 
@@ -417,7 +416,7 @@
 		Int4 zero_x = CmpEQ(x2, Float4(0.0f));
 		Int4 inf_y = IsInf(y2); // Since x2 >= y2, this means x2 == y2 == inf, so we use 45 degrees or pi/4
 		Float4 atan2_theta = arctan_01(y2 / x2, pp);
-		theta += As<Float4>((~zero_x & ~inf_y & non_zero_y & ((O & As<Int4>(half_pi - atan2_theta)) | (~O & (As<Int4>(atan2_theta))))) | // FIXME: Vector select
+		theta += As<Float4>((~zero_x & ~inf_y & ((O & As<Int4>(half_pi - atan2_theta)) | (~O & (As<Int4>(atan2_theta))))) | // FIXME: Vector select
 		                    (inf_y & As<Int4>(quarter_pi)));
 
 		// Recover loss of precision for tiny theta angles
diff --git a/tests/unittests/unittests.cpp b/tests/unittests/unittests.cpp
index 1418e43..3132258 100644
--- a/tests/unittests/unittests.cpp
+++ b/tests/unittests/unittests.cpp
@@ -258,9 +258,12 @@
 		GLint posLoc = glGetAttribLocation(program, "position");
 		EXPECT_GLENUM_EQ(GL_NONE, glGetError());
 
-		GLint location = glGetUniformLocation(program, textureName);
-		ASSERT_NE(-1, location);
-		glUniform1i(location, 0);
+		if(textureName)
+		{
+			GLint location = glGetUniformLocation(program, textureName);
+			ASSERT_NE(-1, location);
+			glUniform1i(location, 0);
+		}
 
 		float vertices[18] = { -1.0f,  1.0f, 0.5f,
 		                       -1.0f, -1.0f, 0.5f,
@@ -368,6 +371,60 @@
 	Uninitialize();
 }
 
+// Test sampling from a sampler in a struct as a function argument
+TEST_F(SwiftShaderTest, AtanCornerCases)
+{
+	Initialize(3, false);
+
+	const std::string vs =
+		"#version 300 es\n"
+		"in vec4 position;\n"
+		"void main()\n"
+		"{\n"
+		"	gl_Position = vec4(position.xy, 0.0, 1.0);\n"
+		"}\n";
+
+	const std::string fs =
+		"#version 300 es\n"
+		"precision mediump float;\n"
+		"const float kPI = 3.14159265358979323846;"
+		"uniform float positive_value;\n"
+		"uniform float negative_value;\n"
+		"out vec4 fragColor;\n"
+		"void main()\n"
+		"{\n"
+		"	// Should yield vec4(0, pi, pi/2, -pi/2)\n"
+		"	vec4 result = atan(vec4(0.0, 0.0, positive_value, negative_value),\n"
+		"	                   vec4(positive_value, negative_value, 0.0, 0.0));\n"
+		"	fragColor = (result / vec4(kPI)) + vec4(0.5, -0.5, 0.0, 1.0) + vec4(0.5 / 255.0);\n"
+		"}\n";
+
+	const ProgramHandles ph = createProgram(vs, fs);
+
+	glUseProgram(ph.program);
+	GLint positive_value = glGetUniformLocation(ph.program, "positive_value");
+	ASSERT_NE(-1, positive_value);
+	GLint negative_value = glGetUniformLocation(ph.program, "negative_value");
+	ASSERT_NE(-1, negative_value);
+	glUniform1f(positive_value,  1.0);
+	glUniform1f(negative_value, -1.0);
+
+	glClearColor(0.0, 0.0, 0.0, 0.0);
+	glClear(GL_COLOR_BUFFER_BIT);
+	EXPECT_GLENUM_EQ(GL_NONE, glGetError());
+
+	drawQuad(ph.program, nullptr);
+
+	deleteProgram(ph);
+
+	unsigned char grey[4] = { 128, 128, 128, 128 };
+	compareColor(grey);
+
+	EXPECT_GLENUM_EQ(GL_NONE, glGetError());
+
+	Uninitialize();
+}
+
 // Note: GL_ARB_texture_rectangle is part of gl2extchromium.h in the Chromium repo
 // GL_ARB_texture_rectangle
 #ifndef GL_ARB_texture_rectangle