diff --git a/src/cmp/cmpc-inliner.lsp b/src/cmp/cmpc-inliner.lsp
index d113a05c7..b8d759e1d 100644
--- a/src/cmp/cmpc-inliner.lsp
+++ b/src/cmp/cmpc-inliner.lsp
@@ -147,6 +147,11 @@
                    (return-from inline-type-matches nil))
                  (push new-type rts)
                  (setq number-max (maximum-float-type number-max new-type))))
+              #+sse2
+              ;; Allow implicit casts between SSE subtypes to kick in
+              ((and (type>= 'ext:sse-pack type)
+                    (type>= 'ext:sse-pack arg-type))
+               (push type rts))
               ((type>= type arg-type)
                (push type rts))
               (t (return-from inline-type-matches nil)))))
diff --git a/src/cmp/cmpffi.lsp b/src/cmp/cmpffi.lsp
index 3c27f8a0a..3ca9ca69c 100644
--- a/src/cmp/cmpffi.lsp
+++ b/src/cmp/cmpffi.lsp
@@ -355,7 +355,20 @@
 	((:int-sse-pack :float-sse-pack :double-sse-pack)
 	 (case loc-rep-type
 	   ((:object)
-	    (wt-from-object-conversion dest-type loc-type dest-rep-type loc))
+	    (wt-from-object-conversion 'ext:sse-pack loc-type dest-rep-type loc))
+           ;; Implicitly cast between SSE subtypes
+           ((:int-sse-pack :float-sse-pack :double-sse-pack)
+            (wt (ecase dest-rep-type
+                  (:int-sse-pack (ecase loc-rep-type
+                                   (:float-sse-pack "_mm_castps_si128")
+                                   (:double-sse-pack "_mm_castpd_si128")))
+                  (:float-sse-pack (ecase loc-rep-type
+                                     (:int-sse-pack "_mm_castsi128_ps")
+                                     (:double-sse-pack "_mm_castpd_ps")))
+                  (:double-sse-pack (ecase loc-rep-type
+                                      (:int-sse-pack "_mm_castsi128_pd")
+                                      (:float-sse-pack "_mm_castps_pd"))))
+                "(" loc ")"))
 	   (otherwise
 	    (coercion-error))))
 	(t
diff --git a/src/h/ecl-inl.h b/src/h/ecl-inl.h
index c4a01079a..7f508986a 100644
--- a/src/h/ecl-inl.h
+++ b/src/h/ecl-inl.h
@@ -54,6 +54,9 @@
   } else do {
 #define end_loop_for_on(list) } while (list = ECL_CONS_CDR(list), ECL_CONSP(list))
 
+/*
+ * Static constant definition.
+ */
 #ifdef __cplusplus
 #define ecl_cast_ptr(type,n) reinterpret_cast<type>((void*)n)
 #else
@@ -117,10 +120,53 @@
         static const cl_object name = (cl_object)(& name ## data)
 
 #ifdef ECL_SSE2
+
+/*
+ * Static SSE constant.
+ */
+
 #define ecl_def_ct_sse_pack(name,type,v0,v1,v2,v3,v4,v5,v6,v7,v8,v9,v10,v11,v12,v13,v14,v15) \
         static const struct ecl_sse_pack name ## data = {                 \
                 (int8_t)t_sse_pack, 0, (type), 0,                         \
                 {{v0,v1,v2,v3,v4,v5,v6,v7,v8,v9,v10,v11,v12,v13,v14,v15}} \
         }; \
         static const cl_object name = (cl_object)(& name ## data)
+
+/*
+ * Missing SSE intrinsics
+ */
+
+#if (defined(__INTEL_COMPILER) ? __INTEL_COMPILER < 810 : defined(_MSC_VER) && (_MSC_VER < 1500))
+
+__forceinline __m128i _mm_castps_si128(__m128 a) { union { __m128 f; __m128i i;} c; c.f = a; return c.i; }
+__forceinline __m128 _mm_castsi128_ps(__m128i a) { union { __m128 f; __m128i i;} c; c.i = a; return c.f; }
+__forceinline __m128i _mm_castpd_si128(__m128d a) { union { __m128d d; __m128i i;} c; c.d = a; return c.i; }
+__forceinline __m128d _mm_castsi128_pd(__m128i a) { union { __m128d d; __m128i i;} c; c.i = a; return c.d; }
+__forceinline __m128d _mm_castps_pd(__m128 a) { union { __m128d d; __m128 f;} c; c.f = a; return c.d; }
+__forceinline __m128 _mm_castpd_ps(__m128d a) { union { __m128d d; __m128 f;} c; c.d = a; return c.f; }
+
+#elif defined(__GNUC__) && (__GNUC__ < 4) && !defined(__INTEL_COMPILER)
+
+// Copied from GCC 4 headers:
+extern __inline __m128 __attribute__((__gnu_inline__, __always_inline__, __artificial__))
+_mm_castpd_ps(__m128d __A) { return (__m128) __A; }
+
+extern __inline __m128i __attribute__((__gnu_inline__, __always_inline__, __artificial__))
+_mm_castpd_si128(__m128d __A) { return (__m128i) __A; }
+
+extern __inline __m128d __attribute__((__gnu_inline__, __always_inline__, __artificial__))
+_mm_castps_pd(__m128 __A) { return (__m128d) __A; }
+
+extern __inline __m128i __attribute__((__gnu_inline__, __always_inline__, __artificial__))
+_mm_castps_si128(__m128 __A) { return (__m128i) __A; }
+
+extern __inline __m128 __attribute__((__gnu_inline__, __always_inline__, __artificial__))
+_mm_castsi128_ps(__m128i __A) { return (__m128) __A; }
+
+extern __inline __m128d __attribute__((__gnu_inline__, __always_inline__, __artificial__))
+_mm_castsi128_pd(__m128i __A) { return (__m128d) __A; }
+
 #endif
+
+#endif /* ECL_SSE2 */
+