diff --git a/lib/files.cf b/lib/files.cf
index d7525bee37..e2853d5ce7 100644
--- a/lib/files.cf
+++ b/lib/files.cf
@@ -437,25 +437,33 @@ bundle edit_line set_variable_values_ini(tab, sectionName)
 
       # Be careful if the index string contains funny chars
       "cindex[$(index)]" string => canonify("$(index)");
+      "_escaped_section" string => escape("$(sectionName)");
 
   classes:
       "edit_$(cindex[$(index)])"     not => strcmp("$($(tab)[$(sectionName)][$(index)])","dontchange"),
       comment => "Create conditions to make changes";
 
+      "section_$(sectionName)_exists"
+        expression => regline("^\[$(_escaped_section)\]", "$(edit.filename)"),
+        if => fileexists("$(edit.filename)"),
+        comment => "Check if the section header already exists in the file";
+
   field_edits:
 
       # If the line is there, but commented out, first uncomment it
       "#+\s*$(index)\s*=.*"
       select_region => INI_section(escape("$(sectionName)")),
       edit_field => col("\s*=\s*","1","$(index)","set"),
-      if => "edit_$(cindex[$(index)])";
+      if => and("edit_$(cindex[$(index)])",
+                canonify("section_$(sectionName)_exists"));
 
       # match a line starting like the key something
       "\s*$(index)\s*=.*"
       edit_field => col("\s*=\s*","2","$($(tab)[$(sectionName)][$(index)])","set"),
       select_region => INI_section(escape("$(sectionName)")),
       classes => results("bundle", "set_variable_values_ini_not_$(cindex[$(index)])"),
-      if => "edit_$(cindex[$(index)])";
+      if => and("edit_$(cindex[$(index)])",
+                canonify("section_$(sectionName)_exists"));
 
   insert_lines:
       "[$(sectionName)]"
@@ -464,7 +472,16 @@ bundle edit_line set_variable_values_ini(tab, sectionName)
 
       "$(index)=$($(tab)[$(sectionName)][$(index)])"
       select_region => INI_section(escape("$(sectionName)")),
-        if => "!(set_variable_values_ini_not_$(cindex[$(index)])_kept|set_variable_values_ini_not_$(cindex[$(index)])_repaired).edit_$(cindex[$(index)])";
+        if => and("!(set_variable_values_ini_not_$(cindex[$(index)])_kept|set_variable_values_ini_not_$(cindex[$(index)])_repaired)",
+                  "edit_$(cindex[$(index)])",
+                  canonify("section_$(sectionName)_exists")),
+        handle => "insert_key_in_existing_section_$(sectionName)_$(cindex[$(index)])";
+
+      "$(index)=$($(tab)[$(sectionName)][$(index)])"
+        location => after("^\[$(_escaped_section)\]"),
+        if => and("edit_$(cindex[$(index)])",
+                  not(canonify("section_$(sectionName)_exists"))),
+        handle => "insert_key_in_new_section_$(sectionName)_$(cindex[$(index)])";
 
 }
 
diff --git a/tests/acceptance/lib/files/set_variable_values_ini_missing_section.cf b/tests/acceptance/lib/files/set_variable_values_ini_missing_section.cf
new file mode 100644
index 0000000000..6671d8af72
--- /dev/null
+++ b/tests/acceptance/lib/files/set_variable_values_ini_missing_section.cf
@@ -0,0 +1,67 @@
+#######################################################
+#
+# Test that set_variable_values_ini does not error when section doesn't exist
+#
+#######################################################
+
+body common control
+{
+      inputs => { "../../default.cf.sub" };
+      bundlesequence  => { default("$(this.promise_filename)") };
+      version => "1.0";
+}
+
+#######################################################
+
+bundle agent init
+{
+  files:
+      # The tested file "actual" is copied from our seeded starting position.
+      "$(G.testfile).actual"
+        copy_from => local_cp("$(this.promise_filename).actual");
+
+      # Next we place the file which we will compare the final result with.
+      "$(G.testfile).expected"
+        copy_from => local_cp("$(this.promise_filename).expected");
+}
+
+#######################################################
+
+bundle agent test
+{
+  meta:
+      "description" -> { "CFE-3866" }
+        string => "Test that set_variable_values_ini does not error when section doesn't exist";
+
+  vars:
+      "config[section1][key1]" string => "value1";
+      "config[section1][key2]" string => "value2";
+      "config[section2][key3]" string => "value3";
+      "config[section2][key4]" string => "value4";
+
+  files:
+      "$(G.testfile).actual"
+        create => "true",
+        edit_line => set_variable_values_ini("test.config", "section1");
+
+      "$(G.testfile).actual"
+        edit_line => set_variable_values_ini("test.config", "section2");
+}
+
+#######################################################
+
+bundle agent check
+{
+  methods:
+      "check"
+        usebundle => dcs_if_diff("$(G.testfile).actual", "$(G.testfile).expected",
+                                 "pass", "_fail");
+
+      "fail"
+        usebundle => dcs_fail($(this.promise_filename)),
+        if => "_fail";
+
+    pass::
+      "pass"
+        usebundle => dcs_pass($(this.promise_filename));
+}
diff --git a/tests/acceptance/lib/files/set_variable_values_ini_missing_section.cf.actual b/tests/acceptance/lib/files/set_variable_values_ini_missing_section.cf.actual
new file mode 100644
index 0000000000..e69de29bb2
diff --git a/tests/acceptance/lib/files/set_variable_values_ini_missing_section.cf.expected b/tests/acceptance/lib/files/set_variable_values_ini_missing_section.cf.expected
new file mode 100644
index 0000000000..4adafa063c
--- /dev/null
+++ b/tests/acceptance/lib/files/set_variable_values_ini_missing_section.cf.expected
@@ -0,0 +1,6 @@
+[section2]
+key3=value3
+key4=value4
+[section1]
+key2=value2
+key1=value1