diff --git a/src/merge.js b/src/merge.js
index 279cc9ed8..e5db76244 100644
--- a/src/merge.js
+++ b/src/merge.js
@@ -180,6 +180,8 @@ class Merge {
         if (doc.size == null) { doc.size = file.size }
         if (doc.class == null) { doc.class = file.class }
         if (doc.mime == null) { doc.mime = file.mime }
+      } else if (!isUpToDate(side, file)) {
+        return this.resolveConflictAsync(side, doc)
       }
       if (sameFile(file, doc)) {
         log.info({doc}, 'up to date')
diff --git a/src/metadata.js b/src/metadata.js
index 556310a7e..2ef1481de 100644
--- a/src/metadata.js
+++ b/src/metadata.js
@@ -182,17 +182,7 @@ export function sameFile (one: Metadata, two: Metadata) {
 
 // Return true if the two files have the same binary content
 export function sameBinary (one: Metadata, two: Metadata) {
-  if ((one.docType !== 'file') || (two.docType !== 'file')) {
-    return false
-  } else if ((one.md5sum != null) && (one.md5sum === two.md5sum)) {
-    return true
-  } else if ((one.remote != null) && (two.remote != null)) {
-    let oneId = one.remote._id
-    let twoId = two.remote._id
-    return (oneId != null) && (oneId === twoId)
-  } else {
-    return false
-  }
+  return one.md5sum === two.md5sum
 }
 
 // Mark the next rev for this side
diff --git a/src/remote/index.js b/src/remote/index.js
index 39c3785a2..184462e17 100644
--- a/src/remote/index.js
+++ b/src/remote/index.js
@@ -119,11 +119,16 @@ export default class Remote implements Side {
   async overwriteFileAsync (doc: Metadata, old: ?Metadata): Promise<Metadata> {
     log.info(`${doc.path}: Uploading new file version...`)
     const stream = await this.other.createReadStreamAsync(doc)
-    const updated = await this.remoteCozy.updateFileById(doc.remote._id, stream, {
+    const options = {
       contentType: doc.mime,
       checksum: doc.md5sum,
-      lastModifiedDate: new Date(doc.updated_at)
-    })
+      lastModifiedDate: new Date(doc.updated_at),
+      ifMatch: ''
+    }
+    if (old && old.remote) {
+      options.ifMatch = old.remote._rev
+    }
+    const updated = await this.remoteCozy.updateFileById(doc.remote._id, stream, options)
 
     doc.remote._rev = updated._rev
 
diff --git a/test/unit/merge.js b/test/unit/merge.js
index 595b2499f..ff9778e3c 100644
--- a/test/unit/merge.js
+++ b/test/unit/merge.js
@@ -146,7 +146,11 @@ describe('Merge', function () {
           path: 'FIZZBUZZ.JPG',
           docType: 'file',
           md5sum: '3333333333333333333333333333333333333333',
-          tags: ['qux', 'quux']
+          tags: ['qux', 'quux'],
+          sides: {
+            local: 2,
+            remote: 2
+          }
         }
         this.merge.updateFileAsync(this.side, clone(doc)).then(() => {
           this.pouch.db.get(this.file._id, function (err, res) {
diff --git a/test/unit/metadata.js b/test/unit/metadata.js
index 9cd89012b..9e867de69 100644
--- a/test/unit/metadata.js
+++ b/test/unit/metadata.js
@@ -325,26 +325,6 @@ describe('metadata', function () {
       ret.should.be.true()
     })
 
-    it('returns true for two docs with the same remote file', function () {
-      let one = {
-        md5sum: 'adc83b19e793491b1c6ea0fd8b46cd9f32e592fc',
-        docType: 'file',
-        remote: {
-          _id: 'f00b4r'
-        }
-      }
-      let two = {
-        docType: 'file',
-        remote: {
-          _id: 'f00b4r'
-        }
-      }
-      let ret = sameBinary(one, two)
-      ret.should.be.true()
-      ret = sameBinary(two, one)
-      ret.should.be.true()
-    })
-
     it('returns false for two different documents', function () {
       let one = {
         docType: 'file',
@@ -357,18 +337,8 @@ describe('metadata', function () {
           _id: 'f00b4r'
         }
       }
-      let three = {
-        docType: 'file',
-        remote: {
-          _id: 'c00463'
-        }
-      }
       let ret = sameBinary(one, two)
       ret.should.be.false()
-      ret = sameBinary(two, three)
-      ret.should.be.false()
-      ret = sameBinary(three, one)
-      ret.should.be.false()
     })
   })