diff --git a/lib/infer/params.js b/lib/infer/params.js
index 4701727a8..b8efa193c 100644
--- a/lib/infer/params.js
+++ b/lib/infer/params.js
@@ -121,11 +121,20 @@ module.exports = function () {
 
         path.value.params.forEach(function (param, j) {
           if (existingParams[param.name] === undefined) {
+            // This type is not explicitly documented
             if (!comment.params) {
               comment.params = [];
             }
 
             comment.params = comment.params.concat(paramToDoc(param, j));
+          } else if (!existingParams[param.name].type) {
+            // This param has a description, but potentially it can
+            // be have an inferred type. Infer its type without
+            // dropping the description.
+            var doc = paramToDoc(param, j);
+            if (doc.type) {
+              existingParams[param.name].type = doc.type;
+            }
           }
           paramOrder[param.name] = i++;
         });
diff --git a/test/fixture/merge-infered-type.input.js b/test/fixture/merge-infered-type.input.js
new file mode 100644
index 000000000..1bdd4ba40
--- /dev/null
+++ b/test/fixture/merge-infered-type.input.js
@@ -0,0 +1,9 @@
+/**
+ * Add five to `x`.
+ *
+ * @param x The number to add five to.
+ * @returns {number} x plus five.
+ */
+function addFive(x: number): number {
+  return x + 5;
+}
diff --git a/test/fixture/merge-infered-type.output.custom.md b/test/fixture/merge-infered-type.output.custom.md
new file mode 100644
index 000000000..e033cf7c6
--- /dev/null
+++ b/test/fixture/merge-infered-type.output.custom.md
@@ -0,0 +1,9 @@
+# addFive
+
+Add five to `x`.
+
+**Parameters**
+
+-   `x` **number** The number to add five to.
+
+Returns **number** x plus five.
diff --git a/test/fixture/merge-infered-type.output.json b/test/fixture/merge-infered-type.output.json
new file mode 100644
index 000000000..26a353c14
--- /dev/null
+++ b/test/fixture/merge-infered-type.output.json
@@ -0,0 +1,82 @@
+[
+  {
+    "description": "Add five to `x`.",
+    "tags": [
+      {
+        "title": "param",
+        "description": "The number to add five to.",
+        "lineNumber": 3,
+        "type": {
+          "type": "NameExpression",
+          "name": "number"
+        },
+        "name": "x"
+      },
+      {
+        "title": "returns",
+        "description": "x plus five.",
+        "lineNumber": 4,
+        "type": {
+          "type": "NameExpression",
+          "name": "number"
+        }
+      }
+    ],
+    "loc": {
+      "start": {
+        "line": 1,
+        "column": 0
+      },
+      "end": {
+        "line": 6,
+        "column": 3
+      }
+    },
+    "context": {
+      "loc": {
+        "start": {
+          "line": 7,
+          "column": 0
+        },
+        "end": {
+          "line": 9,
+          "column": 1
+        }
+      },
+      "code": "/**\n * Add five to `x`.\n *\n * @param x The number to add five to.\n * @returns {number} x plus five.\n */\nfunction addFive(x: number): number {\n  return x + 5;\n}\n"
+    },
+    "errors": [],
+    "params": [
+      {
+        "title": "param",
+        "description": "The number to add five to.",
+        "lineNumber": 3,
+        "type": {
+          "type": "NameExpression",
+          "name": "number"
+        },
+        "name": "x"
+      }
+    ],
+    "returns": [
+      {
+        "title": "returns",
+        "description": "x plus five.",
+        "lineNumber": 4,
+        "type": {
+          "type": "NameExpression",
+          "name": "number"
+        }
+      }
+    ],
+    "name": "addFive",
+    "kind": "function",
+    "members": {
+      "instance": [],
+      "static": []
+    },
+    "path": [
+      "addFive"
+    ]
+  }
+]
\ No newline at end of file
diff --git a/test/fixture/merge-infered-type.output.md b/test/fixture/merge-infered-type.output.md
new file mode 100644
index 000000000..e033cf7c6
--- /dev/null
+++ b/test/fixture/merge-infered-type.output.md
@@ -0,0 +1,9 @@
+# addFive
+
+Add five to `x`.
+
+**Parameters**
+
+-   `x` **number** The number to add five to.
+
+Returns **number** x plus five.
diff --git a/test/fixture/merge-infered-type.output.md.json b/test/fixture/merge-infered-type.output.md.json
new file mode 100644
index 000000000..3dde4a8b3
--- /dev/null
+++ b/test/fixture/merge-infered-type.output.md.json
@@ -0,0 +1,206 @@
+{
+  "type": "root",
+  "children": [
+    {
+      "depth": 1,
+      "type": "heading",
+      "children": [
+        {
+          "type": "text",
+          "value": "addFive"
+        }
+      ]
+    },
+    {
+      "type": "paragraph",
+      "children": [
+        {
+          "type": "text",
+          "value": "Add five to ",
+          "position": {
+            "start": {
+              "line": 1,
+              "column": 1
+            },
+            "end": {
+              "line": 1,
+              "column": 13
+            },
+            "indent": []
+          }
+        },
+        {
+          "type": "inlineCode",
+          "value": "x",
+          "position": {
+            "start": {
+              "line": 1,
+              "column": 13
+            },
+            "end": {
+              "line": 1,
+              "column": 16
+            },
+            "indent": []
+          }
+        },
+        {
+          "type": "text",
+          "value": ".",
+          "position": {
+            "start": {
+              "line": 1,
+              "column": 16
+            },
+            "end": {
+              "line": 1,
+              "column": 17
+            },
+            "indent": []
+          }
+        }
+      ],
+      "position": {
+        "start": {
+          "line": 1,
+          "column": 1
+        },
+        "end": {
+          "line": 1,
+          "column": 17
+        },
+        "indent": []
+      }
+    },
+    {
+      "type": "strong",
+      "children": [
+        {
+          "type": "text",
+          "value": "Parameters"
+        }
+      ]
+    },
+    {
+      "ordered": false,
+      "type": "list",
+      "children": [
+        {
+          "type": "listItem",
+          "children": [
+            {
+              "type": "paragraph",
+              "children": [
+                {
+                  "type": "inlineCode",
+                  "value": "x"
+                },
+                {
+                  "type": "text",
+                  "value": " "
+                },
+                {
+                  "type": "strong",
+                  "children": [
+                    {
+                      "type": "text",
+                      "value": "number"
+                    }
+                  ]
+                },
+                {
+                  "type": "text",
+                  "value": " "
+                },
+                {
+                  "type": "paragraph",
+                  "children": [
+                    {
+                      "type": "text",
+                      "value": "The number to add five to.",
+                      "position": {
+                        "start": {
+                          "line": 1,
+                          "column": 1
+                        },
+                        "end": {
+                          "line": 1,
+                          "column": 27
+                        },
+                        "indent": []
+                      }
+                    }
+                  ],
+                  "position": {
+                    "start": {
+                      "line": 1,
+                      "column": 1
+                    },
+                    "end": {
+                      "line": 1,
+                      "column": 27
+                    },
+                    "indent": []
+                  }
+                }
+              ]
+            }
+          ]
+        }
+      ]
+    },
+    {
+      "type": "paragraph",
+      "children": [
+        {
+          "type": "text",
+          "value": "Returns "
+        },
+        {
+          "type": "strong",
+          "children": [
+            {
+              "type": "text",
+              "value": "number"
+            }
+          ]
+        },
+        {
+          "type": "text",
+          "value": " "
+        },
+        {
+          "type": "paragraph",
+          "children": [
+            {
+              "type": "text",
+              "value": "x plus five.",
+              "position": {
+                "start": {
+                  "line": 1,
+                  "column": 1
+                },
+                "end": {
+                  "line": 1,
+                  "column": 13
+                },
+                "indent": []
+              }
+            }
+          ],
+          "position": {
+            "start": {
+              "line": 1,
+              "column": 1
+            },
+            "end": {
+              "line": 1,
+              "column": 13
+            },
+            "indent": []
+          }
+        }
+      ]
+    }
+  ]
+}
\ No newline at end of file