diff --git a/src/spicy/manager.cc b/src/spicy/manager.cc
index 9ad40b10ad..1a9420e22a 100644
--- a/src/spicy/manager.cc
+++ b/src/spicy/manager.cc
@@ -897,14 +897,21 @@ void Manager::disableReplacedAnalyzers() {
         if ( file_mgr->Lookup(replaces, false) || packet_mgr->Lookup(replaces, false) )
             reporter->FatalError("cannot replace '%s' analyzer with a protocol analyzer", replaces);
 
-        auto tag = analyzer_mgr->GetAnalyzerTag(replaces);
-        if ( ! tag ) {
+        auto component = analyzer_mgr->Lookup(replaces, false);
+        if ( ! component ) {
             SPICY_DEBUG(hilti::rt::fmt("%s is supposed to replace protocol analyzer %s, but that does not exist",
                                        info.name_analyzer, replaces));
 
             continue;
         }
 
+        auto tag = component->Tag();
+        if ( analyzer_mgr->HasComponentMapping(tag) )
+            reporter->FatalError(
+                "%s: protocol analyzer %s is already mapped to a different analyzer; cannot replace an analyzer "
+                "multiple times",
+                info.name_analyzer.c_str(), component->Name().c_str());
+
         SPICY_DEBUG(hilti::rt::fmt("%s replaces existing protocol analyzer %s", info.name_analyzer, replaces));
         info.replaces = tag;
         analyzer_mgr->DisableAnalyzer(tag);
@@ -928,10 +935,17 @@ void Manager::disableReplacedAnalyzers() {
             continue;
         }
 
+        auto tag = component->Tag();
+        if ( file_mgr->HasComponentMapping(tag) )
+            reporter->FatalError(
+                "%s: file analyzer %s is already mapped to a different analyzer; cannot replace an analyzer multiple "
+                "times",
+                info.name_analyzer.c_str(), component->Name().c_str());
+
         SPICY_DEBUG(hilti::rt::fmt("%s replaces existing file analyzer %s", info.name_analyzer, replaces));
-        info.replaces = component->Tag();
+        info.replaces = tag;
         component->SetEnabled(false);
-        file_mgr->AddComponentMapping(component->Tag(), info.tag);
+        file_mgr->AddComponentMapping(tag, info.tag);
     }
 
     for ( auto& info : _packet_analyzers_by_type ) {
@@ -948,10 +962,17 @@ void Manager::disableReplacedAnalyzers() {
             continue;
         }
 
+        auto tag = component->Tag();
+        if ( packet_mgr->HasComponentMapping(tag) )
+            reporter->FatalError(
+                "%s: packet analyzer %s is already mapped to a different analyzer; cannot replace an analyzer multiple "
+                "times",
+                info.name_analyzer.c_str(), component->Name().c_str());
+
         SPICY_DEBUG(hilti::rt::fmt("%s replaces existing packet analyzer %s", info.name_analyzer, replaces));
-        info.replaces = component->Tag();
+        info.replaces = tag;
         component->SetEnabled(false);
-        packet_mgr->AddComponentMapping(component->Tag(), info.tag);
+        packet_mgr->AddComponentMapping(tag, info.tag);
     }
 }
 
diff --git a/testing/btest/Baseline/spicy.replaces-conflicts-2/output b/testing/btest/Baseline/spicy.replaces-conflicts-2/output
new file mode 100644
index 0000000000..b4f454e6e7
--- /dev/null
+++ b/testing/btest/Baseline/spicy.replaces-conflicts-2/output
@@ -0,0 +1,2 @@
+### BTest baseline data generated by btest-diff. Do not edit. Use "btest -U/-u" to update. Requires BTest >= 0.63.
+fatal error: spicy::SSH_2: file analyzer MD5 is already mapped to a different analyzer; cannot replace an analyzer multiple times
diff --git a/testing/btest/Baseline/spicy.replaces-conflicts-3/output b/testing/btest/Baseline/spicy.replaces-conflicts-3/output
new file mode 100644
index 0000000000..0733458438
--- /dev/null
+++ b/testing/btest/Baseline/spicy.replaces-conflicts-3/output
@@ -0,0 +1,2 @@
+### BTest baseline data generated by btest-diff. Do not edit. Use "btest -U/-u" to update. Requires BTest >= 0.63.
+fatal error: spicy::SSH_2: packet analyzer Ethernet is already mapped to a different analyzer; cannot replace an analyzer multiple times
diff --git a/testing/btest/Baseline/spicy.replaces-conflicts/output b/testing/btest/Baseline/spicy.replaces-conflicts/output
new file mode 100644
index 0000000000..8cf95b5195
--- /dev/null
+++ b/testing/btest/Baseline/spicy.replaces-conflicts/output
@@ -0,0 +1,2 @@
+### BTest baseline data generated by btest-diff. Do not edit. Use "btest -U/-u" to update. Requires BTest >= 0.63.
+fatal error: redefinition of protocol analyzer spicy::SSH_1
diff --git a/testing/btest/spicy/replaces-conflicts.evt b/testing/btest/spicy/replaces-conflicts.evt
new file mode 100644
index 0000000000..dbca6d637e
--- /dev/null
+++ b/testing/btest/spicy/replaces-conflicts.evt
@@ -0,0 +1,42 @@
+# @TEST-REQUIRES: have-spicy
+#
+# @TEST-EXEC: spicyz -d -o ssh.hlto ssh.spicy %INPUT
+# @TEST-EXEC-FAIL: zeek ssh.hlto >output 2>&1
+# @TEST-EXEC: btest-diff output
+
+# @TEST-START-FILE ssh.spicy
+module SSH;
+
+import zeek;
+
+public type Banner = unit {};
+# @TEST-END-FILE
+
+protocol analyzer spicy::SSH_1 over TCP:
+    parse with SSH::Banner,
+    replaces SSH;
+
+protocol analyzer spicy::SSH_1 over UDP:
+    parse with SSH::Banner,
+    replaces SSH;
+
+# @TEST-START-NEXT
+
+file analyzer spicy::SSH_1:
+    parse with SSH::Banner,
+    replaces MD5;
+
+file analyzer spicy::SSH_2:
+    parse with SSH::Banner,
+    replaces MD5;
+
+# @TEST-START-NEXT
+
+packet analyzer spicy::SSH_1:
+    parse with SSH::Banner,
+    replaces Ethernet;
+
+packet analyzer spicy::SSH_2:
+    parse with SSH::Banner,
+    replaces Ethernet;
+