diff --git a/c/mapping/mapper_put.c b/c/mapping/mapper_put.c
index e49075bed..684229631 100644
--- a/c/mapping/mapper_put.c
+++ b/c/mapping/mapper_put.c
@@ -117,7 +117,7 @@ static mapper_t* mapper_put_parse_cli(int* pargi, int argc, char** argv) {
 	int   print_ast                           = FALSE;
 	int   trace_parse                         = FALSE;
 	char* oosvar_flatten_separator            = DEFAULT_OOSVAR_FLATTEN_SEPARATOR;
-	int   flush_every_record                  = FALSE;
+	int   flush_every_record                  = TRUE;
 
 	ap_state_t* pstate = ap_alloc();
 	ap_define_string_flag(pstate,    "-f", &expression_filename);
@@ -172,15 +172,15 @@ static mapper_t* mapper_put_alloc(ap_state_t* pargp, char* mlr_dsl_expression,
 	// Retain the string contents along with any in-pointers from the AST/CST
 	pstate->mlr_dsl_expression = mlr_dsl_expression;
 	pstate->comment_stripped_mlr_dsl_expression = comment_stripped_mlr_dsl_expression;
-	pstate->past         = past;
-	pstate->pcst         = mlr_dsl_cst_alloc(past, type_inferencing);
-	pstate->at_begin     = TRUE;
-	pstate->outer_filter = outer_filter;
-	pstate->poosvars     = mlhmmv_alloc();
+	pstate->past                     = past;
+	pstate->pcst                     = mlr_dsl_cst_alloc(past,   type_inferencing);
+	pstate->at_begin                 = TRUE;
+	pstate->outer_filter             = outer_filter;
+	pstate->poosvars                 = mlhmmv_alloc();
 	pstate->oosvar_flatten_separator = oosvar_flatten_separator;
-	pstate->flush_every_record = flush_every_record;
-	pstate->pbind_stack  = bind_stack_alloc();
-	pstate->ploop_stack  = loop_stack_alloc();
+	pstate->flush_every_record       = flush_every_record;
+	pstate->pbind_stack              = bind_stack_alloc();
+	pstate->ploop_stack              = loop_stack_alloc();
 
 	mapper_t* pmapper      = mlr_malloc_or_die(sizeof(mapper_t));
 	pmapper->pvstate       = (void*)pstate;
diff --git a/c/reg_test/expected/out b/c/reg_test/expected/out
index a20297649..f41486f00 100644
--- a/c/reg_test/expected/out
+++ b/c/reg_test/expected/out
@@ -27334,6 +27334,62 @@ hat cat 44.325655 88    0.503701
 hat dog 37.114244 78    0.475824
 
 
+================================================================
+MAPPER TEE
+
+mlr --from ./reg_test/input/abixy tee ./output/tee1/out then nothing
+
+mlr cat -n ./output/tee1/out
+n=1,a=pan,b=pan,i=1,x=0.3467901443380824,y=0.7268028627434533
+n=2,a=eks,b=pan,i=2,x=0.7586799647899636,y=0.5221511083334797
+n=3,a=wye,b=wye,i=3,x=0.20460330576630303,y=0.33831852551664776
+n=4,a=eks,b=wye,i=4,x=0.38139939387114097,y=0.13418874328430463
+n=5,a=wye,b=pan,i=5,x=0.5732889198020006,y=0.8636244699032729
+n=6,a=zee,b=pan,i=6,x=0.5271261600918548,y=0.49322128674835697
+n=7,a=eks,b=zee,i=7,x=0.6117840605678454,y=0.1878849191181694
+n=8,a=zee,b=wye,i=8,x=0.5985540091064224,y=0.976181385699006
+n=9,a=hat,b=wye,i=9,x=0.03144187646093577,y=0.7495507603507059
+n=10,a=pan,b=wye,i=10,x=0.5026260055412137,y=0.9526183602969864
+
+mlr --from ./reg_test/input/abixy tee --no-fflush ./output/tee1/out then nothing
+
+mlr cat -n ./output/tee1/out
+n=1,a=pan,b=pan,i=1,x=0.3467901443380824,y=0.7268028627434533
+n=2,a=eks,b=pan,i=2,x=0.7586799647899636,y=0.5221511083334797
+n=3,a=wye,b=wye,i=3,x=0.20460330576630303,y=0.33831852551664776
+n=4,a=eks,b=wye,i=4,x=0.38139939387114097,y=0.13418874328430463
+n=5,a=wye,b=pan,i=5,x=0.5732889198020006,y=0.8636244699032729
+n=6,a=zee,b=pan,i=6,x=0.5271261600918548,y=0.49322128674835697
+n=7,a=eks,b=zee,i=7,x=0.6117840605678454,y=0.1878849191181694
+n=8,a=zee,b=wye,i=8,x=0.5985540091064224,y=0.976181385699006
+n=9,a=hat,b=wye,i=9,x=0.03144187646093577,y=0.7495507603507059
+n=10,a=pan,b=wye,i=10,x=0.5026260055412137,y=0.9526183602969864
+
+mlr --from ./reg_test/input/abixy tee -a ./output/tee1/out then nothing
+
+mlr cat -n ./output/tee1/out
+n=1,a=pan,b=pan,i=1,x=0.3467901443380824,y=0.7268028627434533
+n=2,a=eks,b=pan,i=2,x=0.7586799647899636,y=0.5221511083334797
+n=3,a=wye,b=wye,i=3,x=0.20460330576630303,y=0.33831852551664776
+n=4,a=eks,b=wye,i=4,x=0.38139939387114097,y=0.13418874328430463
+n=5,a=wye,b=pan,i=5,x=0.5732889198020006,y=0.8636244699032729
+n=6,a=zee,b=pan,i=6,x=0.5271261600918548,y=0.49322128674835697
+n=7,a=eks,b=zee,i=7,x=0.6117840605678454,y=0.1878849191181694
+n=8,a=zee,b=wye,i=8,x=0.5985540091064224,y=0.976181385699006
+n=9,a=hat,b=wye,i=9,x=0.03144187646093577,y=0.7495507603507059
+n=10,a=pan,b=wye,i=10,x=0.5026260055412137,y=0.9526183602969864
+n=11,a=pan,b=pan,i=1,x=0.3467901443380824,y=0.7268028627434533
+n=12,a=eks,b=pan,i=2,x=0.7586799647899636,y=0.5221511083334797
+n=13,a=wye,b=wye,i=3,x=0.20460330576630303,y=0.33831852551664776
+n=14,a=eks,b=wye,i=4,x=0.38139939387114097,y=0.13418874328430463
+n=15,a=wye,b=pan,i=5,x=0.5732889198020006,y=0.8636244699032729
+n=16,a=zee,b=pan,i=6,x=0.5271261600918548,y=0.49322128674835697
+n=17,a=eks,b=zee,i=7,x=0.6117840605678454,y=0.1878849191181694
+n=18,a=zee,b=wye,i=8,x=0.5985540091064224,y=0.976181385699006
+n=19,a=hat,b=wye,i=9,x=0.03144187646093577,y=0.7495507603507059
+n=20,a=pan,b=wye,i=10,x=0.5026260055412137,y=0.9526183602969864
+
+
 ================================================================
 OOSVAR-FROM-SREC ASSIGNMENT
 
diff --git a/c/reg_test/run b/c/reg_test/run
index a07621f0b..3a14498e9 100755
--- a/c/reg_test/run
+++ b/c/reg_test/run
@@ -3467,7 +3467,7 @@ run_mlr cat -n $tee1/out
 #run_mlr cat -n $tee2/out.pan
 #run_mlr cat -n $tee2/out.wye
 #run_mlr cat -n $tee2/out.zee
-#
+
 ## ----------------------------------------------------------------
 #announce DSL PRINT
 #