diff --git a/src/script_opt/ScriptOpt.cc b/src/script_opt/ScriptOpt.cc
index 937671a600..347b0d3348 100644
--- a/src/script_opt/ScriptOpt.cc
+++ b/src/script_opt/ScriptOpt.cc
@@ -508,6 +508,8 @@ static void analyze_scripts_for_ZAM(std::unique_ptr<ProfileFuncs>& pfs)
 
 	if ( ! did_one )
 		reporter->FatalError("no matching functions/files for -O ZAM");
+
+	finalize_functions(funcs);
 	}
 
 void analyze_scripts()
diff --git a/src/script_opt/ZAM/AM-Opt.cc b/src/script_opt/ZAM/AM-Opt.cc
index f32ccf1fc4..3593da3dc5 100644
--- a/src/script_opt/ZAM/AM-Opt.cc
+++ b/src/script_opt/ZAM/AM-Opt.cc
@@ -18,7 +18,7 @@ namespace zeek::detail
 // can't do this when compiling individual functions since for event handlers
 // and hooks it needs to be computed across all of their bodies.
 //
-// Note, this is now not really needed, because we no longer use any
+// Note, this is now not actually needed, because we no longer use any
 // interpreter frame entries other than those for the function's arguments.
 // We keep the code in case that changes, for example when deciding to
 // compile functions that include "return when" conditions.
@@ -26,40 +26,39 @@ std::unordered_map<const Func*, int> remapped_intrp_frame_sizes;
 
 void finalize_functions(const std::vector<FuncInfo>& funcs)
 	{
-	// Given we've now compiled all of the function bodies, we
-	// can reset the interpreter frame sizes of each function
-	// to be the maximum needed to accommodate all of its
-	// remapped bodies.
+	// Given we've now compiled all of the function bodies, we can reset
+	// the interpreter frame sizes to what's actually used.  This can be
+	// a huge win for massively inlined event handlers, which otherwise
+	// can have frames sized for 100s of variables, none of which (other
+	// than the arguments) need TLC such as via calls to Frame::Reset().
 
 	// Find any functions with bodies that weren't compiled and
-	// make sure we don't reduce their frame size.  For any loaded
-	// from ZAM save files, use the associated maximum interpreter
-	// frame size as a minimum.
+	// make sure we don't reduce their frame size.
+	std::unordered_set<const Func*> leave_alone;
+
+	for ( auto& f : funcs )
+		if ( f.Body()->Tag() != STMT_ZAM )
+			// This function has a body that wasn't compiled,
+			// don't mess with its size.
+			leave_alone.insert(f.Func());
+
 	for ( auto& f : funcs )
 		{
 		auto func = f.Func();
 
-		// If we have non-compiled versions of the function's body,
-		// preserve the size they need.
-		int size = func->FrameSize();
-
-		if ( f.Body()->Tag() != STMT_ZAM && remapped_intrp_frame_sizes.count(func) > 0 &&
-		     size > remapped_intrp_frame_sizes[func] )
-			remapped_intrp_frame_sizes[func] = size;
-		}
-
-	for ( auto& f : funcs )
-		{
-		auto func = f.Func();
+		if ( leave_alone.count(func) > 0 )
+			continue;
 
 		if ( remapped_intrp_frame_sizes.count(func) == 0 )
 			// No entry for this function, keep current frame size.
 			continue;
 
-		// Note, functions with multiple bodies appear in "funcs"
-		// multiple times, but the following doesn't hurt to do
-		// more than once.
-		func->SetFrameSize(remapped_intrp_frame_sizes[func]);
+		auto& ft = func->GetType();
+		auto& params = ft->Params();
+		func->SetFrameSize(params->NumFields());
+
+		// Don't bother processing any future instances.
+		leave_alone.insert(func);
 		}
 	}
 
diff --git a/src/script_opt/ZAM/ZBody.h b/src/script_opt/ZAM/ZBody.h
index 3e39bc8b03..11699a848b 100644
--- a/src/script_opt/ZAM/ZBody.h
+++ b/src/script_opt/ZAM/ZBody.h
@@ -34,8 +34,8 @@ public:
 	~ZBody() override;
 
 	// These are split out from the constructor to allow construction
-	// of a ZBody from either save-file full instructions (first method)
-	// or intermediary instructions (second method).
+	// of a ZBody from either save-file full instructions (first method,
+	// not currently supported) or intermediary instructions (second method).
 	void SetInsts(std::vector<ZInst*>& insts);
 	void SetInsts(std::vector<ZInstI*>& instsI);