diff --git a/main.cpp b/main.cpp
index 2ec1f9a8..3af1c776 100644
--- a/main.cpp
+++ b/main.cpp
@@ -91,7 +91,7 @@ static void usage(int ret) {
     printf("        disable-gather-scatter-flattening\tDisable flattening when all lanes are on\n");
     printf("        disable-uniform-memory-optimizations\tDisable uniform-based coherent memory access\n");
     printf("        disable-masked-store-optimizations\tDisable lowering to regular stores when possible\n");
-    printf("    [--target={sse2,sse4,sse4x2,avx}] Select target ISA (SSE4 is default)\n");
+    printf("    [--target={sse2,sse4,sse4x2,avx}] Select target ISA (SSE4 is default unless compiling for atom; then SSE2 is.)\n");
     printf("    [--version]\t\t\t\tPrint ispc version\n");
     printf("    [--woff]\t\t\t\tDisable warnings\n");
     printf("    [--wno-perf]\t\t\tDon't issue warnings related to performance-related issues\n");
@@ -192,7 +192,7 @@ int main(int Argc, char *Argv[]) {
     // as we're parsing below
     g = new Globals;
 
-    bool debugSet = false, optSet = false;
+    bool debugSet = false, optSet = false, targetSet = false;
     Module::OutputType ot = Module::Object;
 
     for (int i = 1; i < argc; ++i) {
@@ -226,6 +226,7 @@ int main(int Argc, char *Argv[]) {
         else if (!strcmp(argv[i], "--target")) {
             if (++i == argc) usage(1);
             lDoTarget(argv[i]);
+            targetSet = true;
         }
         else if (!strncmp(argv[i], "--target=", 9)) {
             const char *target = argv[i] + 9;
@@ -315,6 +316,11 @@ int main(int Argc, char *Argv[]) {
     if (debugSet && !optSet)
         g->opt.level = 0;
 
+    // Make SSE2 the default target on atom unless the target has been set
+    // explicitly.
+    if (!targetSet && (g->target.cpu == "atom"))
+        lDoTarget("sse2");
+
     m = new Module(file);
     if (m->CompileFile() == 0) {
         if (outFileName != NULL)