diff --git a/src/Expr.cc b/src/Expr.cc
index 88c2bbd759..bfb6b17be6 100644
--- a/src/Expr.cc
+++ b/src/Expr.cc
@@ -3139,6 +3139,12 @@ static bool expand_op_elem(ListExprPtr elems, ExprPtr elem, TypePtr t) {
             return false;
         }
 
+        // If this expands to nothing, assume that is important and don't expand.
+        if ( v->AsTableVal()->Size() == 0 ) {
+            elems->Append(elem);
+            return false;
+        }
+
         for ( auto& s_elem : v->AsTableVal()->ToMap() ) {
             auto c_elem = with_location_of(make_intrusive<ConstExpr>(s_elem.first), elem);
             elems->Append(expand_one_elem(index_exprs, yield, c_elem, set_offset));
diff --git a/testing/btest/Baseline/language.init-mismatch/.stderr b/testing/btest/Baseline/language.init-mismatch/.stderr
index 294a1efe24..b9f4335a16 100644
--- a/testing/btest/Baseline/language.init-mismatch/.stderr
+++ b/testing/btest/Baseline/language.init-mismatch/.stderr
@@ -5,17 +5,25 @@ error in <...>/init-mismatch.zeek, line 7: Initialization not preceded by =<...>
 error in <...>/init-mismatch.zeek, line 13: different number of indices (list of count,count and list of count,count,count)
 error in <...>/init-mismatch.zeek, line 14: table constructor element lacks '=' structure (bar)
 error in <...>/init-mismatch.zeek, line 17: empty list in untyped initialization ()
-error in <...>/init-mismatch.zeek, line 23: cannot expand constructor elements using a value that depends on local variables (subnets)
-error in <...>/init-mismatch.zeek, line 23: type clash in assignment (my_subnets = set(foo, subnets))
-error in <...>/init-mismatch.zeek, line 26: requires arithmetic operands (c + 2, 4)
-error in <...>/init-mismatch.zeek, line 27: constructor list not allowed for -= operations on vectors (v -= 3, 5)
-error in <...>/init-mismatch.zeek, line 29: RHS type mismatch for table/set += (s1 += s2)
-error in <...>/init-mismatch.zeek, line 30: RHS type mismatch for table/set -= (s1 -= s2)
-error in <...>/init-mismatch.zeek, line 32: table constructor used in a non-table context (3 = F)
-error in double and <...>/init-mismatch.zeek, line 32: arithmetic mixed with non-arithmetic (double and 3 = F)
-error in <...>/init-mismatch.zeek, line 32 and double: type mismatch (3 = F and double)
-error in <...>/init-mismatch.zeek, line 32: inconsistent type in set constructor (set(3 = F))
-error in <...>/init-mismatch.zeek, line 34: not a list of indices (s2)
-error in <...>/init-mismatch.zeek, line 34: type clash in assignment (s3 = set(s2))
-error in <...>/init-mismatch.zeek, line 36: pattern += op requires op to be a pattern (p += 3)
-error in <...>/init-mismatch.zeek, line 38: illegal table constructor element (1.2.3.4)
+error in <...>/init-mismatch.zeek, line 21: type clash (set[count] and set())
+error in <...>/init-mismatch.zeek, line 21: type mismatch (set() and set[count])
+error in <...>/init-mismatch.zeek, line 21: inconsistent type in set constructor (set(set()))
+error in <...>/init-mismatch.zeek, line 21: type clash in assignment (s4 = set(set()))
+error in <...>/init-mismatch.zeek, line 22: type clash (vector of count and vector())
+error in <...>/init-mismatch.zeek, line 22: type mismatch (vector() and vector of count)
+error in <...>/init-mismatch.zeek, line 22: inconsistent type in set constructor (set(vector()))
+error in <...>/init-mismatch.zeek, line 22: type clash in assignment (s5 = set(vector()))
+error in <...>/init-mismatch.zeek, line 28: cannot expand constructor elements using a value that depends on local variables (subnets)
+error in <...>/init-mismatch.zeek, line 28: type clash in assignment (my_subnets = set(foo, subnets))
+error in <...>/init-mismatch.zeek, line 31: requires arithmetic operands (c + 2, 4)
+error in <...>/init-mismatch.zeek, line 32: constructor list not allowed for -= operations on vectors (v -= 3, 5)
+error in <...>/init-mismatch.zeek, line 34: RHS type mismatch for table/set += (s1 += s2)
+error in <...>/init-mismatch.zeek, line 35: RHS type mismatch for table/set -= (s1 -= s2)
+error in <...>/init-mismatch.zeek, line 37: table constructor used in a non-table context (3 = F)
+error in double and <...>/init-mismatch.zeek, line 37: arithmetic mixed with non-arithmetic (double and 3 = F)
+error in <...>/init-mismatch.zeek, line 37 and double: type mismatch (3 = F and double)
+error in <...>/init-mismatch.zeek, line 37: inconsistent type in set constructor (set(3 = F))
+error in <...>/init-mismatch.zeek, line 39: not a list of indices (s2)
+error in <...>/init-mismatch.zeek, line 39: type clash in assignment (s3 = set(s2))
+error in <...>/init-mismatch.zeek, line 41: pattern += op requires op to be a pattern (p += 3)
+error in <...>/init-mismatch.zeek, line 43: illegal table constructor element (1.2.3.4)
diff --git a/testing/btest/Baseline/language.set/out b/testing/btest/Baseline/language.set/out
index c53cae332c..c3e47d607c 100644
--- a/testing/btest/Baseline/language.set/out
+++ b/testing/btest/Baseline/language.set/out
@@ -99,3 +99,5 @@ pattern index reduced size (PASS)
 pattern index iteration (PASS)
 pattern index JSON roundtrip success (PASS)
 pattern index JSON roundtrip correct (PASS)
+empty set gets added with multiple types (PASS)
+empty vector gets added with multiple types (PASS)
diff --git a/testing/btest/language/init-mismatch.zeek b/testing/btest/language/init-mismatch.zeek
index 2153ca6efd..b260646d37 100644
--- a/testing/btest/language/init-mismatch.zeek
+++ b/testing/btest/language/init-mismatch.zeek
@@ -16,6 +16,11 @@ global v: vector of count;
 global p: pattern;
 global x = { };
 
+# Issue #3933: For sets that contain a list and another set, expansion should behave
+# a bit more conservatively. That means the inner [] are impactful
+global s4: set[set[count]] = { [ set() ] };
+global s5: set[vector of count] = { [ vector() ] };
+
 function foo()
 	{
 	local subnets = { 1.2.3.4/24, 2.3.4.5/5 };
diff --git a/testing/btest/language/set.zeek b/testing/btest/language/set.zeek
index 24e2ce402c..c90f7f1db0 100644
--- a/testing/btest/language/set.zeek
+++ b/testing/btest/language/set.zeek
@@ -294,6 +294,16 @@ function complex_index_type_pattern()
 	test_case( "pattern index JSON roundtrip correct", to_json(s) == to_json(fjr$v) );
 }
 
+# Issue 3933: Sets defined with an empty container and {[]} were silently discarding
+# the inner set.
+function with_empty_containers()
+	{
+	local simple_set: set[count, set[count]] = { [ 1, set() ] };
+	test_case("empty set gets added with multiple types", |simple_set| == 1);
+	local simple_vec: set[count, vector of count] = { [ 1, vector() ] };
+	test_case("empty vector gets added with multiple types", |simple_vec| == 1);
+	}
+
 event zeek_init()
 {
 	basic_functionality();
@@ -301,4 +311,5 @@ event zeek_init()
 	complex_index_type_vector();
 	complex_index_type_set();
 	complex_index_type_pattern();
+	with_empty_containers();
 }