diff --git a/src/Magnum/MultisampleTexture.h b/src/Magnum/MultisampleTexture.h
index 64b57a7aa..35f132213 100644
--- a/src/Magnum/MultisampleTexture.h
+++ b/src/Magnum/MultisampleTexture.h
@@ -40,9 +40,10 @@ namespace Magnum {
 
 namespace Implementation {
     template<UnsignedInt> constexpr GLenum multisampleTextureTarget();
-    template<> constexpr GLenum multisampleTextureTarget<2>() { return GL_TEXTURE_2D_MULTISAMPLE; }
+    /* GCC 4.5 doesn't have constexpr, so it needs inline */
+    template<> constexpr inline GLenum multisampleTextureTarget<2>() { return GL_TEXTURE_2D_MULTISAMPLE; }
     #ifndef MAGNUM_TARGET_GLES
-    template<> constexpr GLenum multisampleTextureTarget<3>() { return GL_TEXTURE_2D_MULTISAMPLE_ARRAY; }
+    template<> constexpr inline GLenum multisampleTextureTarget<3>() { return GL_TEXTURE_2D_MULTISAMPLE_ARRAY; }
     #endif
 
     template<UnsignedInt dimensions> typename DimensionTraits<dimensions, Int>::VectorType maxMultisampleTextureSize();
diff --git a/src/Magnum/Texture.h b/src/Magnum/Texture.h
index 3bfc75139..d1d1b8af9 100644
--- a/src/Magnum/Texture.h
+++ b/src/Magnum/Texture.h
@@ -40,11 +40,12 @@ namespace Magnum {
 
 namespace Implementation {
     template<UnsignedInt> constexpr GLenum textureTarget();
+    /* GCC 4.5 doesn't have constexpr, so it needs inline */
     #ifndef MAGNUM_TARGET_GLES
-    template<> constexpr GLenum textureTarget<1>() { return GL_TEXTURE_1D; }
+    template<> constexpr inline GLenum textureTarget<1>() { return GL_TEXTURE_1D; }
     #endif
-    template<> constexpr GLenum textureTarget<2>() { return GL_TEXTURE_2D; }
-    template<> constexpr GLenum textureTarget<3>() {
+    template<> constexpr inline GLenum textureTarget<2>() { return GL_TEXTURE_2D; }
+    template<> constexpr inline GLenum textureTarget<3>() {
         #ifndef MAGNUM_TARGET_GLES2
         return GL_TEXTURE_3D;
         #else
diff --git a/src/Magnum/TextureArray.h b/src/Magnum/TextureArray.h
index c6568a1f3..fd4a81892 100644
--- a/src/Magnum/TextureArray.h
+++ b/src/Magnum/TextureArray.h
@@ -41,10 +41,11 @@ namespace Magnum {
 
 namespace Implementation {
     template<UnsignedInt> constexpr GLenum textureArrayTarget();
+    /* GCC 4.5 doesn't have constexpr, so it needs inline */
     #ifndef MAGNUM_TARGET_GLES
-    template<> constexpr GLenum textureArrayTarget<1>() { return GL_TEXTURE_1D_ARRAY; }
+    template<> constexpr inline GLenum textureArrayTarget<1>() { return GL_TEXTURE_1D_ARRAY; }
     #endif
-    template<> constexpr GLenum textureArrayTarget<2>() { return GL_TEXTURE_2D_ARRAY; }
+    template<> constexpr inline GLenum textureArrayTarget<2>() { return GL_TEXTURE_2D_ARRAY; }
 }
 
 /**