diff --git a/dlls/wined3d/glsl_shader.c b/dlls/wined3d/glsl_shader.c
index d82d24c1c6a..90062b8b000 100644
--- a/dlls/wined3d/glsl_shader.c
+++ b/dlls/wined3d/glsl_shader.c
@@ -1346,6 +1346,27 @@ void shader_glsl_pow(SHADER_OPCODE_ARG *arg) {
     }
 }
 
+/* Process the WINED3DSIO_LOG instruction in GLSL (dst = log2(|src0|))
+ * Src0 is a scalar. Note that D3D uses the absolute of src0, while
+ * GLSL uses the value as-is. */
+void shader_glsl_log(SHADER_OPCODE_ARG *arg) {
+    SHADER_BUFFER *buffer = arg->buffer;
+    glsl_src_param_t src0_param;
+    DWORD dst_write_mask;
+    size_t dst_size;
+
+    dst_write_mask = shader_glsl_append_dst(buffer, arg);
+    dst_size = shader_glsl_get_write_mask_size(dst_write_mask);
+
+    shader_glsl_add_src_param(arg, arg->src[0], arg->src_addr[0], WINED3DSP_WRITEMASK_0, &src0_param);
+
+    if (dst_size > 1) {
+        shader_addline(buffer, "vec%d(log2(abs(%s))));\n", dst_size, src0_param.param_str);
+    } else {
+        shader_addline(buffer, "log2(abs(%s)));\n", src0_param.param_str);
+    }
+}
+
 /* Map the opcode 1-to-1 to the GL code (arg->dst = instruction(src0, src1, ...) */
 void shader_glsl_map2gl(SHADER_OPCODE_ARG* arg) {
     CONST SHADER_OPCODE* curOpcode = arg->opcode;
diff --git a/dlls/wined3d/pixelshader.c b/dlls/wined3d/pixelshader.c
index 245c6b0142f..8b2977bec4d 100644
--- a/dlls/wined3d/pixelshader.c
+++ b/dlls/wined3d/pixelshader.c
@@ -167,7 +167,7 @@ CONST SHADER_OPCODE IWineD3DPixelShaderImpl_shader_ins[] = {
     {WINED3DSIO_SGE,  "sge",  "SGE", 1, 3, pshader_hw_map2gl, shader_glsl_compare, 0, 0},
     {WINED3DSIO_ABS,  "abs",  "ABS", 1, 2, pshader_hw_map2gl, shader_glsl_map2gl, 0, 0},
     {WINED3DSIO_EXP,  "exp",  "EX2", 1, 2, pshader_hw_map2gl, shader_glsl_map2gl, 0, 0},
-    {WINED3DSIO_LOG,  "log",  "LG2", 1, 2, pshader_hw_map2gl, shader_glsl_map2gl, 0, 0},
+    {WINED3DSIO_LOG,  "log",  "LG2", 1, 2, pshader_hw_map2gl, shader_glsl_log, 0, 0},
     {WINED3DSIO_EXPP, "expp", "EXP", 1, 2, pshader_hw_map2gl, shader_glsl_expp, 0, 0},
     {WINED3DSIO_LOGP, "logp", "LOG", 1, 2, pshader_hw_map2gl, shader_glsl_map2gl, 0, 0},
     {WINED3DSIO_DST,  "dst",  "DST", 1, 3, pshader_hw_map2gl, shader_glsl_dst, 0, 0},
diff --git a/dlls/wined3d/wined3d_private.h b/dlls/wined3d/wined3d_private.h
index 1cfd6223db0..da4a90c2608 100644
--- a/dlls/wined3d/wined3d_private.h
+++ b/dlls/wined3d/wined3d_private.h
@@ -1839,6 +1839,7 @@ extern void shader_glsl_call(SHADER_OPCODE_ARG* arg);
 extern void shader_glsl_callnz(SHADER_OPCODE_ARG* arg);
 extern void shader_glsl_label(SHADER_OPCODE_ARG* arg);
 extern void shader_glsl_pow(SHADER_OPCODE_ARG* arg);
+extern void shader_glsl_log(SHADER_OPCODE_ARG* arg);
 extern void shader_glsl_texldl(SHADER_OPCODE_ARG* arg);
 
 /** GLSL Pixel Shader Prototypes */