diff --git a/src/main/java/org/prebid/server/bidder/mobkoi/MobkoiBidder.java b/src/main/java/org/prebid/server/bidder/mobkoi/MobkoiBidder.java
index dbf82da1b4f..699f9dca4c6 100644
--- a/src/main/java/org/prebid/server/bidder/mobkoi/MobkoiBidder.java
+++ b/src/main/java/org/prebid/server/bidder/mobkoi/MobkoiBidder.java
@@ -75,14 +75,14 @@ private ExtImpMobkoi parseExtImp(Imp imp) {
     }
 
     private Imp modifyImp(Imp firstImp, ExtImpMobkoi extImpMobkoi) {
-        if (StringUtils.isNotBlank(firstImp.getTagid())) {
-            return firstImp;
-        }
-
         if (StringUtils.isNotBlank(extImpMobkoi.getPlacementId())) {
             return firstImp.toBuilder().tagid(extImpMobkoi.getPlacementId()).build();
         }
 
+        if (StringUtils.isNotBlank(firstImp.getTagid())) {
+            return firstImp;
+        }
+
         throw new PreBidException("invalid because it comes with neither request.imp[0].tagId nor "
                     + "req.imp[0].ext.Bidder.placementId");
     }
diff --git a/src/test/java/org/prebid/server/bidder/mobkoi/MobkoiBidderTest.java b/src/test/java/org/prebid/server/bidder/mobkoi/MobkoiBidderTest.java
index 7d46ce2a0a8..1b559e579b7 100644
--- a/src/test/java/org/prebid/server/bidder/mobkoi/MobkoiBidderTest.java
+++ b/src/test/java/org/prebid/server/bidder/mobkoi/MobkoiBidderTest.java
@@ -95,6 +95,38 @@ public void makeHttpRequestsShouldAddPlacementIdOnlyInFirstImpressionTagId() {
                 .containsExactly("pid", null);
     }
 
+    @Test
+    public void makeHttpRequestsShouldOverrideExistingTagIdWithPlacementId() {
+        final ObjectNode mobkoiExt = impExt("placement-id-from-ext");
+        final Imp givenImp1 = givenImp(impBuilder -> impBuilder.tagid("existing-tag-id").ext(mobkoiExt));
+        final Imp givenImp2 = givenImp(identity());
+        final BidRequest bidRequest = BidRequest.builder().imp(asList(givenImp1, givenImp2)).build();
+        final Result<List<HttpRequest<BidRequest>>> result = target.makeHttpRequests(bidRequest);
+
+        assertThat(result.getValue())
+                .extracting(httpRequest -> mapper.readValue(httpRequest.getBody(), BidRequest.class))
+                .flatExtracting(BidRequest::getImp)
+                .extracting(imp -> imp.getTagid())
+                .containsExactly("placement-id-from-ext", null);
+        assertThat(result.getErrors()).isEmpty();
+    }
+
+    @Test
+    public void makeHttpRequestsShouldKeepExistingTagIdWhenPlacementIdIsMissing() {
+        final ObjectNode mobkoiExt = impExt(null);
+        final Imp givenImp1 = givenImp(impBuilder -> impBuilder.tagid("existing-tag-id").ext(mobkoiExt));
+        final Imp givenImp2 = givenImp(identity());
+        final BidRequest bidRequest = BidRequest.builder().imp(asList(givenImp1, givenImp2)).build();
+        final Result<List<HttpRequest<BidRequest>>> result = target.makeHttpRequests(bidRequest);
+
+        assertThat(result.getValue())
+                .extracting(httpRequest -> mapper.readValue(httpRequest.getBody(), BidRequest.class))
+                .flatExtracting(BidRequest::getImp)
+                .extracting(imp -> imp.getTagid())
+                .containsExactly("existing-tag-id", null);
+        assertThat(result.getErrors()).isEmpty();
+    }
+
     @Test
     public void makeHttpRequestsShouldOverrideUserExtAndSetConsent() {
         // given