diff --git a/packages/babel-cli/test/fixtures/babel/dir --out-dir --source-maps inline/out-files/lib/foo.js b/packages/babel-cli/test/fixtures/babel/dir --out-dir --source-maps inline/out-files/lib/foo.js
index 3537587fad..b85deb8a28 100644
--- a/packages/babel-cli/test/fixtures/babel/dir --out-dir --source-maps inline/out-files/lib/foo.js	
+++ b/packages/babel-cli/test/fixtures/babel/dir --out-dir --source-maps inline/out-files/lib/foo.js	
@@ -3,4 +3,4 @@
 arr.map(function (x) {
   return x * MULTIPLIER;
 });
-//# sourceMappingURL=data:application/json;base64,eyJ2ZXJzaW9uIjozLCJzb3VyY2VzIjpbIi4uL3NyYy9mb28uanMiXSwibmFtZXMiOltdLCJtYXBwaW5ncyI6Ijs7QUFBQSxHQUFHLENBQUMsR0FBRyxDQUFDLFVBQUEsQ0FBQztTQUFJLENBQUMsR0FBRyxVQUFVO0NBQUEsQ0FBQyxDQUFDIiwiZmlsZSI6ImZvby5qcyIsInNvdXJjZXNDb250ZW50IjpbImFyci5tYXAoeCA9PiB4ICogTVVMVElQTElFUik7Il19
+//# sourceMappingURL=data:application/json;base64,eyJ2ZXJzaW9uIjozLCJzb3VyY2VzIjpbIi4uL3NyYy9mb28uanMiXSwibmFtZXMiOltdLCJtYXBwaW5ncyI6Ijs7QUFBQSxHQUFHLENBQUMsR0FBRyxDQUFDLFdBQUM7U0FBSSxDQUFDLEdBQUcsVUFBVTtFQUFDLENBQUMiLCJmaWxlIjoiZm9vLmpzIiwic291cmNlc0NvbnRlbnQiOlsiYXJyLm1hcCh4ID0+IHggKiBNVUxUSVBMSUVSKTsiXX0=
diff --git a/packages/babel-cli/test/fixtures/babel/dir --out-dir --source-maps/out-files/lib/foo.js.map b/packages/babel-cli/test/fixtures/babel/dir --out-dir --source-maps/out-files/lib/foo.js.map
index 77300ca29a..8a97ef8479 100644
--- a/packages/babel-cli/test/fixtures/babel/dir --out-dir --source-maps/out-files/lib/foo.js.map	
+++ b/packages/babel-cli/test/fixtures/babel/dir --out-dir --source-maps/out-files/lib/foo.js.map	
@@ -1 +1 @@
-{"version":3,"sources":["../src/foo.js"],"names":[],"mappings":";;AAAA,GAAG,CAAC,GAAG,CAAC,UAAA,CAAC;SAAI,CAAC,GAAG,UAAU;CAAA,CAAC,CAAC","file":"foo.js","sourcesContent":["arr.map(x => x * MULTIPLIER);"]}
+{"version":3,"sources":["../src/foo.js"],"names":[],"mappings":";;AAAA,GAAG,CAAC,GAAG,CAAC,WAAC;SAAI,CAAC,GAAG,UAAU;EAAC,CAAC","file":"foo.js","sourcesContent":["arr.map(x => x * MULTIPLIER);"]}
diff --git a/packages/babel-cli/test/fixtures/babel/filename --out-file --source-maps inline/out-files/script2.js b/packages/babel-cli/test/fixtures/babel/filename --out-file --source-maps inline/out-files/script2.js
index 31da0b4f1a..a7d0097e5f 100644
--- a/packages/babel-cli/test/fixtures/babel/filename --out-file --source-maps inline/out-files/script2.js	
+++ b/packages/babel-cli/test/fixtures/babel/filename --out-file --source-maps inline/out-files/script2.js	
@@ -4,4 +4,4 @@ arr.map(function (x) {
   return x * MULTIPLIER;
 });
 
-//# sourceMappingURL=data:application/json;base64,eyJ2ZXJzaW9uIjozLCJzb3VyY2VzIjpbInNjcmlwdC5qcyJdLCJuYW1lcyI6W10sIm1hcHBpbmdzIjoiOztBQUFBLEdBQUcsQ0FBQyxHQUFHLENBQUMsVUFBQSxDQUFDO1NBQUksQ0FBQyxHQUFHLFVBQVU7Q0FBQSxDQUFDLENBQUMiLCJmaWxlIjoic2NyaXB0Mi5qcyIsInNvdXJjZXNDb250ZW50IjpbImFyci5tYXAoeCA9PiB4ICogTVVMVElQTElFUik7Il19
+//# sourceMappingURL=data:application/json;base64,eyJ2ZXJzaW9uIjozLCJzb3VyY2VzIjpbInNjcmlwdC5qcyJdLCJuYW1lcyI6W10sIm1hcHBpbmdzIjoiOztBQUFBLEdBQUcsQ0FBQyxHQUFHLENBQUMsV0FBQztTQUFJLENBQUMsR0FBRyxVQUFVO0VBQUMsQ0FBQyIsImZpbGUiOiJzY3JpcHQyLmpzIiwic291cmNlc0NvbnRlbnQiOlsiYXJyLm1hcCh4ID0+IHggKiBNVUxUSVBMSUVSKTsiXX0=
diff --git a/packages/babel-cli/test/fixtures/babel/filenames --out-file --source-maps inline/out-files/script3.js b/packages/babel-cli/test/fixtures/babel/filenames --out-file --source-maps inline/out-files/script3.js
index a32030e61a..6f597b3783 100644
--- a/packages/babel-cli/test/fixtures/babel/filenames --out-file --source-maps inline/out-files/script3.js	
+++ b/packages/babel-cli/test/fixtures/babel/filenames --out-file --source-maps inline/out-files/script3.js	
@@ -11,4 +11,4 @@ arr.map(function (x) {
   return x * MULTIPLIER;
 });
 
-//# sourceMappingURL=data:application/json;base64,eyJ2ZXJzaW9uIjozLCJzb3VyY2VzIjpbInNjcmlwdC5qcyIsInNjcmlwdDIuanMiXSwibmFtZXMiOltdLCJtYXBwaW5ncyI6Ijs7OztJQUFNLElBQUksWUFBSixJQUFJO3dCQUFKLElBQUk7Ozs7O0FDQVYsR0FBRyxDQUFDLEdBQUcsQ0FBQyxVQUFBLENBQUM7U0FBSSxDQUFDLEdBQUcsVUFBVTtDQUFBLENBQUMsQ0FBQyIsImZpbGUiOiJzY3JpcHQzLmpzIiwic291cmNlc0NvbnRlbnQiOlsiY2xhc3MgVGVzdCB7XG5cbn0iLCJhcnIubWFwKHggPT4geCAqIE1VTFRJUExJRVIpOyJdfQ==
+//# sourceMappingURL=data:application/json;base64,eyJ2ZXJzaW9uIjozLCJzb3VyY2VzIjpbInNjcmlwdC5qcyIsInNjcmlwdDIuanMiXSwibmFtZXMiOltdLCJtYXBwaW5ncyI6Ijs7OztJQUFNLElBQUksWUFBSixJQUFJO3dCQUFKLElBQUk7Ozs7O0FDQVYsR0FBRyxDQUFDLEdBQUcsQ0FBQyxXQUFDO1NBQUksQ0FBQyxHQUFHLFVBQVU7RUFBQyxDQUFDIiwiZmlsZSI6InNjcmlwdDMuanMiLCJzb3VyY2VzQ29udGVudCI6WyJjbGFzcyBUZXN0IHtcblxufSIsImFyci5tYXAoeCA9PiB4ICogTVVMVElQTElFUik7Il19
diff --git a/packages/babel-cli/test/fixtures/babel/filenames --out-file --source-maps/out-files/script3.js.map b/packages/babel-cli/test/fixtures/babel/filenames --out-file --source-maps/out-files/script3.js.map
index 941e54cb54..d408aa06b1 100644
--- a/packages/babel-cli/test/fixtures/babel/filenames --out-file --source-maps/out-files/script3.js.map	
+++ b/packages/babel-cli/test/fixtures/babel/filenames --out-file --source-maps/out-files/script3.js.map	
@@ -1 +1 @@
-{"version":3,"sources":["script.js","script2.js"],"names":[],"mappings":";;;;IAAM,IAAI,YAAJ,IAAI;wBAAJ,IAAI;;;;;ACAV,GAAG,CAAC,GAAG,CAAC,UAAA,CAAC;SAAI,CAAC,GAAG,UAAU;CAAA,CAAC,CAAC","file":"script3.js","sourcesContent":["class Test {\n\n}","arr.map(x => x * MULTIPLIER);"]}
+{"version":3,"sources":["script.js","script2.js"],"names":[],"mappings":";;;;IAAM,IAAI,YAAJ,IAAI;wBAAJ,IAAI;;;;;ACAV,GAAG,CAAC,GAAG,CAAC,WAAC;SAAI,CAAC,GAAG,UAAU;EAAC,CAAC","file":"script3.js","sourcesContent":["class Test {\n\n}","arr.map(x => x * MULTIPLIER);"]}
diff --git a/packages/babel-core/test/fixtures/transformation/source-maps/full/source-map.json b/packages/babel-core/test/fixtures/transformation/source-maps/full/source-map.json
index b2b351d8bb..0495ac768b 100644
--- a/packages/babel-core/test/fixtures/transformation/source-maps/full/source-map.json
+++ b/packages/babel-core/test/fixtures/transformation/source-maps/full/source-map.json
@@ -3,6 +3,6 @@
   "file": "source-maps/full/expected.js",
   "sources": ["source-maps/full/actual.js"],
   "names": [],
-  "mappings": "AAAA,GAAG,CAAC,GAAG,CAAC,UAAA,CAAC;SAAI,CAAC,GAAG,CAAC;CAAA,CAAC,CAAC",
+  "mappings": "AAAA,GAAG,CAAC,GAAG,CAAC,WAAC;SAAI,CAAC,GAAG,CAAC;EAAC,CAAC",
   "sourcesContent": ["arr.map(x => x * x);"]
 }
diff --git a/packages/babel-core/test/fixtures/transformation/source-maps/inline/expected.js b/packages/babel-core/test/fixtures/transformation/source-maps/inline/expected.js
index f93d2fbb34..847e47e539 100644
--- a/packages/babel-core/test/fixtures/transformation/source-maps/inline/expected.js
+++ b/packages/babel-core/test/fixtures/transformation/source-maps/inline/expected.js
@@ -1,4 +1,4 @@
 arr.map(function (x) {
   return x * x;
 });
-//# sourceMappingURL=data:application/json;base64,eyJ2ZXJzaW9uIjozLCJzb3VyY2VzIjpbInNvdXJjZS1tYXBzL2lubGluZS9hY3R1YWwuanMiXSwibmFtZXMiOltdLCJtYXBwaW5ncyI6IkFBQUEsR0FBRyxDQUFDLEdBQUcsQ0FBQyxVQUFBLENBQUM7U0FBSSxDQUFDLEdBQUcsQ0FBQztDQUFBLENBQUMsQ0FBQyIsImZpbGUiOiJzb3VyY2UtbWFwcy9pbmxpbmUvZXhwZWN0ZWQuanMiLCJzb3VyY2VzQ29udGVudCI6WyJhcnIubWFwKHggPT4geCAqIHgpOyJdfQ==
+//# sourceMappingURL=data:application/json;base64,eyJ2ZXJzaW9uIjozLCJzb3VyY2VzIjpbInNvdXJjZS1tYXBzL2lubGluZS9hY3R1YWwuanMiXSwibmFtZXMiOltdLCJtYXBwaW5ncyI6IkFBQUEsR0FBRyxDQUFDLEdBQUcsQ0FBQyxXQUFDO1NBQUksQ0FBQyxHQUFHLENBQUM7RUFBQyxDQUFDIiwiZmlsZSI6InNvdXJjZS1tYXBzL2lubGluZS9leHBlY3RlZC5qcyIsInNvdXJjZXNDb250ZW50IjpbImFyci5tYXAoeCA9PiB4ICogeCk7Il19
diff --git a/packages/babel-generator/src/source-map.js b/packages/babel-generator/src/source-map.js
index f1b3ee3727..0734edef85 100644
--- a/packages/babel-generator/src/source-map.js
+++ b/packages/babel-generator/src/source-map.js
@@ -9,6 +9,7 @@ export default class SourceMap {
   constructor(position, opts, code) {
     this.position = position;
     this.opts     = opts;
+    this.last     = {generated: {}, original: {}};
 
     if (opts.sourceMaps) {
       this.map = new sourceMap.SourceMapGenerator({
@@ -57,10 +58,25 @@ export default class SourceMap {
 
     let original = loc[type];
 
-    map.addMapping({
+    // Avoid emitting duplicates on either side. Duplicated
+    // original values creates unnecesssarily large source maps
+    // and increases compile time. Duplicates on the generated
+    // side can lead to incorrect mappings.
+    if (comparePosition(original, this.last.original)
+        || comparePosition(generated, this.last.generated)) {
+      return;
+    }
+
+    this.last = {
       source: this.opts.sourceFileName,
       generated: generated,
       original: original
-    });
+    };
+
+    map.addMapping(this.last);
   }
 }
+
+function comparePosition(a, b) {
+  return a.line === b.line &&  a.column === b.column;
+}